Open Geospatial Consortium

Submission Date: 2020-04-01

Approval Date: 2020-11-26

Publication Date: 2021-08-04

External identifier of this OGC® document: http://www.opengis.net/doc/is/sensorthings/1.1

URL for this OGC® document: https://docs.ogc.org/is/18-088/18-088.html

Additional Formats (informative): pdf

Please refer to the errata for this document,
which may include some normative corrections.

Internal reference number of this OGC® document: 18-088

Version: 1.1

Category: OGC® Implementation Standard

Editors: Steve Liang, Tania Khalafbeigi, Hylke van der Schaaf

OGC SensorThings API Part 1: Sensing Version 1.1

Copyright notice

Copyright © 2021 Open Geospatial Consortium

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Warning

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Document type: OGC® Standard

Document subtype:

Document stage: Approved

Document language: English

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Table of Contents

Table of Figures

  • Figure 1 - IoT Reference Model (adapted from [ITU-T Y.2060])

  • Figure 2 - Sensing Entities

  • Figure 3 - MultiDatastream Extension Entities

  • Figure 4 - Creating Observations using MQTT publish, and receive notifications for Observations with MQTT

  • Figure 5 - Sequence diagram for receiving updates using MQTT subscribe

Table of Tables

  • Table 1 - SensorThings API Sensing entities and equivalent concepts in O&M 2.0

  • Table 2 - Common control information

  • Table 3 - Properties of a Thing entity

  • Table 4 - Direct relation between a Thing entity and other entity types

  • Table 5 - Properties of a Location entity

  • Table 6 - Direct relation between a Location entity and other entity types

  • Table 7 - List of some code values used for identifying types for the encodingType of the Location and FeatureOfInterest entity

  • Table 8 - Properties of a HistoricalLocation entity

  • Table 9 - Direct relation between an HistoricalLocation entity and other entity types

  • Table 10 - Properties of a Datastream entity

  • Table 11 - Direct relation between a Datastream entity and other entity types

  • Table 12 - List of some code values used for identifying types defined in the O&M conceptual model (OGC 10-004r3 and ISO 19156:2011 Clause 8.2.2)

  • Table 13 - Properties of a Sensor entity

  • Table 14 - Direct relation between a Sensor entity and other entity types

  • Table 15 - List of some code values used for identifying types for the encodingType of the Sensor entity

  • Table 16 - Properties of an ObservedProperty entity

  • Table 17 - Direct relation between an ObservedProperty entity and other entity types

  • Table 18 - Properties of an Observation entity

  • Table 19 - Direct relation between an Observation entity and other entity types

  • Table 20 - Properties of a FeatureOfInterest entity

  • Table 21 - Direct relation between a FeatureOfInterest entity and other entity types

  • Table 22 - Built-in Filter Operators

  • Table 23 - Built-in Query Functions

  • Table 24 - Integrity constraints when creating an entity

  • Table 25 - Integrity constraints when deleting an entity

  • Table 26 - Properties of a MultiDatastream entity

  • Table 27 - Direct relation between a MultiDatastream entity and other entity types

  • Table 28 - Direct relation between an MultiDatastream’s Observation entity and other entity types

Table of Requirements

Abstract

The OGC SensorThings API provides an open, geospatial-enabled and unified way to interconnect the Internet of Things (IoT) devices, data, and applications over the web. At a high level the OGC SensorThings API provides two main functionalities and each function is handled by a part. The two parts are the Sensing part and the Tasking part. The Sensing part provides a standard way to manage and retrieve observations and metadata from heterogeneous IoT sensor systems. This document is version 1.1 and it is extending the first version of Sensing part.

Keywords

The following are keywords to be used by search engines and document catalogues.

ogcdoc, ogc document, iot, internet of things, sensor things, sensors, swe, sensor webs, sensor web enablement, sensor networks

Preface

The OGC SensorThings API provides an open, geospatial-enabled and unified way to interconnect the Internet of Things devices, data, and applications over the web. The OGC SensorThings API is an open Standard, and that means it is non-proprietary, platform-independent, and perpetually royalty-free. Although it is a new Standard, it builds on a rich set of proven-working and widely-adopted open standards, such as the web protocols and the OGC Sensor Web Enablement (SWE) Standards, including the OGC/ISO Observation and Measurement data model [OGC 10-004r3 and ISO 19156:2011]. That also means the OGC SensorThings API is extensible and can be applied to not only simple but also complex use cases.

At a high level the OGC SensorThings API provides two main functionalities and each function is handled by a part. The two parts are the Part I - Sensing and the Part II - Tasking. The Sensing part provides a standard way to manage and retrieve observations and metadata from heterogeneous IoT sensor systems. The Tasking part provides a standard way for parameterizing - also called tasking - of task-able IoT devices, such as sensors or actuators.

The Sensing part provides functions similar to the OGC Sensor Observation Service (SOS) and the Tasking part provides functions similar to the OGC Sensor Planning Service (SPS). The main difference between the SensorThings API and the OGC SOS and SPS is that the SensorThings API is designed specifically for the resource-constrained IoT devices and the web developer community. As a result, the SensorThings API follows the REST principles, the use of an efficient JSON encoding, the use of MQTT protocol, and the use of the flexible OASIS OData protocol and URL conventions.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. The Open Geospatial Consortium shall not be held responsible for identifying any or all such patent rights.

recipients of this document are requested to submit, with their comments, notification of any relevant patent claims or other intellectual property rights of which they may be aware that might be infringed by any implementation of the standard set forth in this document, and to provide supporting documentation.

Changes in version 1.1

Version 1.1 of the SensorThings API is an update to version 1.0 that is (mostly) backwards compatible with version 1.0. Besides the many small clarifications, the main changes are as follows.

  • All entities (except for HistoricalLocation) now have a field of the type JSON Object, named properties or parameters. In version 1.0 such a field already existed for the Thing entity (named properties), and for the Observation entity (named parameters). These fields proved to be extremely useful for storing additional structured meta data used in many domains, that could also be used in filters. Now, all entities except for HistoricalLocation have such a very useful property, whereby in the Observation entity it retains the name parameters.

  • The service root page now shows the requirements that the server implements and allows extensions to expose additional settings. This allows users to easily see exactly which extensions and optional features a server implements. The MQTT extension can now list the MQTT endpoints on the root page, so that a user can discover those endpoints.

  • MQTT topics now must start with the version number of the specification. There were differences between server implementations, with some requiring the version number prefix and others not. This change will fix those incompatibilities from this version on.

The first two changes add extra fields to the JSON returned by the server and should not influence clients made for version 1.0, as most client will ignore any fields they do not know. The second change may cause some minor issues for some clients that are not using the version prefix in MQTT topics, but those clients would already have issues connecting to any server that does use the version prefix in MQTT topics.

This version supersedes the previous version of the OGC SensorThings API Part 1: Sensing (OGC 15-078r6).

Submitting organizations

The following organizations submitted this document to the Open Geospatial Consortium (OGC):

  • University of Calgary, Canada

  • SensorUp Inc., Canada

  • CGI Group Inc., USA

  • Keys, USA

  • DataCove e.U., Austria

  • Fraunhofer-Gesellschaft, Germany

Submitters

All questions regarding this submission should be directed to the editors or the submitters:

Name Representing OGC Member

Steve Liang

University of Calgary, Canada / SensorUp Inc.

Yes

Tania Khalafbeigi

University of Calgary, Canada / SensorUp Inc.

Yes

Hylke van der Schaaf

Fraunhofer, Germany

Yes

Brian Miles

CGI Federal

Yes

Katharina Schleidt

DataCove e.U.

Yes

Sylvain Grellet

BRGM, France

Yes

Mickael Beaufils

BRGM, France

Yes

Marcus Alzona

Keys

Yes

1. Scope

The OGC SensorThings API provides an open Standard-based and geospatial-enabled framework to interconnect the Internet of Things devices, data, and applications over the web.

2. Conformance

Conformance with this Standard shall be checked using all the relevant tests specified in annex a (normative) of this document. The framework, concepts, and methodology for testing, and the criteria to be achieved to claim conformance are specified in the OGC Compliance Testing Policies and Procedures and the OGC Compliance Testing web site1.

All requirements-classes and conformance-classes described in this document are owned by the standard(s) identified.

The following table list the requirements classes defined by this Standard.

Note
 The text in the Requirements class id and Requirements columns in the following table is the path fragment that, when appended to the URI: http://www.opengis.net/spec/iot_sensing/1.1/, provides the URI that can be used to unambiguously identify the requirement and the conformance class.
Requirements class id Requirements Description

req/datamodel/thing

Thing entity

req/datamodel/location

Location entity

req/datamodel/historical-location

HistoricalLocation entity

req/datamodel/datastream

Datastream entity

req/datamodel/sensor

Sensor Entity

req/datamodel/observed-property

ObservedProperty entity

req/datamodel/observation

Observation entity

req/datamodel/feature-of-interest

FeatureOfInterest entity

req/datamodel/entity-control-information

Entities’ common control information

req/resource-path

Addressing to the entities of the SensorThings API service

req/request-data

Requesting data with system query options

req/create-update-delete

Creating, updating, and deleting entities

req/batch-request

Processing multiple requests with a single request

req/multi-datastream

Handling complex observations with complex results, especially when the result is an array.

req/data-array

Serving Observations with the efficient data array encoding

req/create-observations-via-mqtt

creating observations through MQTT

req/receive-updates-via-mqtt

Receiving updates through MQTT

3. References

The following normative documents contain provisions that, through reference in this text, constitute provisions of this document. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. For undated references, the latest edition of the normative document referred to applies.

  • ISO 8601:2004 Data elements and interchange formats – Information interchange - Representation of dates and times, 2004

  • OGC 10-004r3 and ISO 19156:2011(E), OGC Abstract Specification Topic 20: Geographic information — Observations and Measurements, 2011

  • OASIS OData Version 4.0 Part 1: Protocol Plus Errata 02

  • OASIS OData Version 4.0 Part 2: URL Conventions Plus Errata 02

  • OASIS OData JSON Format Version 4.0 Plus Errata 02

  • OASIS OData ABNF Construction Rules Errata 02

  • RFC 2046, Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types

  • RFC 2616, Hypertext Transfer Protocol — HTTP/1.1

  • RFC 4627, the application/json Media Type for Javascript Object Notation (JSON), July 2006

  • Unified Code for Units of Measure (UCUM) – Version 1.9, April 2015

4. Terms and Definitions

This document uses the terms defined in Sub-clause 5.3 of [OGC 06-121r8], which is based on the ISO/IEC Directives, Part 2, Rules for the structure and drafting of International Standards. In particular, the word “shall” (not “must”) is the verb form used to indicate a requirement to be strictly followed to conform to this standard.

For the purposes of this document, the following additional terms and definitions apply.

4.1. Collection

Sets of Resources, which can be retrieved in whole or in part. [RFC5023]

4.2. Entity

Entities are instances of entity types. [OASIS OData Version 4.0 Part 1: Protocol Plus Errata 02]

Note: Thing, Sensor, Datastream, Observation are some example entity types of the OGC SensorThings API.

4.3. Entity sets

Entity sets are named collections of entities (e.g., Sensors is an entity set containing Sensor entities). An entity’s key uniquely identifies the entity within an entity set. Entity sets provide entry points into an OGC SensorThings API service. [OASIS OData Version 4.0 Part 1: Protocol Plus Errata 02]

4.4. (Internet of) Thing

A thing is an object of the physical world (physical things) or the information world (virtual things) that is capable of being identified and integrated into communication networks. [ITU-T Y.2060]

4.5. Measurement

A set of operations having the object of determining the value of a quantity. [OGC 10-004r3 / ISO 19156:2011]

4.6. Observation

Act of measuring or otherwise determining the value of a property. [OGC 10-004r3 / ISO 19156:2011]

4.7. Observation Result

Estimate of the value of a property determined through a known observation procedure. [OGC 10-004r3 / ISO 19156:2011]

4.8. Resource

A network-accessible data object or service identified by an URI, as defined in [RFC 2616]

4.9. REST

The Representational State Transfer (REST) style is an abstraction of the architectural elements within a distributed hypermedia system. REST focuses on the roles of components, the constraints upon their interaction with other components, and their interpretation of significant data elements. It encompasses the fundamental constraints upon components, connectors, and data that define the basis of the Web architecture, and thus the essence of its behavior as a network-based application. An API that conforms to the REST architectural principles/constraints is called a RESTful API.

4.10. Sensor

An entity capable of observing a phenomenon and returning an observed value. Type of observation procedure that provides the estimated value of an observed property at its output. [OGC 12-000]

5. Conventions

This sections provides details and examples for any conventions used in the document. Examples of conventions are symbols, abbreviations, use of XML schema, or special notes regarding how to read the document.

5.1. Presentation of Requirements and Recommendations

Requirements are presented using the following style:

Req [number]

<requirement text>

<requirement id>

<number> is a unique number within the document.

<requirement text> is the requirement itself. Normative verbs like SHALL are written in capitals.

The text at the bottom of the box <requirement id> is the path and it provides the URI of the requirement which can be used to unambiguously identify the requirement.

5.2. Identifiers

The normative provisions in this specification are denoted by the URI

http://www.opengis.net/spec/iot_sensing/1.1/

All requirements and conformance tests that appear in this document are denoted by partial URIs which are relative to this base.

6. Symbols (and abbreviated terms)

API

Application Programming Interface

CS-W

Catalog Service Web

CRUD

Create, Read, Update, and Delete

GML

Geography Markup Language

HTML

HyperText Markup Language

HTTP

Hypertext Transfer Protocol

IoT

Internet of Things

ISO

International Organization for Standardization

JSON

JavaScript Object Notation

OData

the Open Data Protocol

OGC

Open Geospatial Consortium

OWS

OGC Web Services

O&M

Observations and Measurements

REST

REpresentational State Transfer

SensorML

Sensor Model Language

SOS

Sensor Observation Service

SPS

Sensor Planning Service

SWE

Sensor Web Enablement

UCUM

Unified Code for Units of Measure

UML

Unified Modeling Language

WoT

Web of Things

XML

eXtensible Markup Language

7. SensorThings API overview

7.1. Who should use the OGC SensorThings API

Organizations that need web-based platforms to manage, store, share, and analyze IoT-based sensor observation data should use the OGC SensorThings API. The OGC SensorThings API simplifies and accelerates the development of IoT applications. Application developers can use this open Standard to connect to various IoT devices and create innovative applications without worrying the daunting heterogeneous protocols of the different IoT devices, gateways and services. IoT device manufacturers can also use OGC SensorThings API as the API can be embedded within various IoT hardware and software platforms, so that the various IoT devices can effortlessly connect with the OGC Standard-compliant servers around the world. In summary, the OGC SensorThings API is transforming the numerous disjointed IoT systems into a fully connected platform where complex tasks can be synchronized and performed.

7.2. Benefits of the OGC SensorThings API

In today’s world, most IoT devices (e.g., sensors and actuators) have proprietary software interfaces defined by their manufacturers and used selectively. New APIs are often required and developed on an as-needed basis, often in an environment with resource limitations and associated risks. This situation requires significant investment on the part of developers for each new sensor or project involving multiple systems and on the part of the providers of sensors, gateways, and portals or services where observations and measurements are required.

As a standardized data model and interface for sensors in the WoT and IoT2, the OGC SensorThings API offers the following benefits: (1) it permits the proliferation of new high value services with lower overhead of development and wider reach, (2) it lowers the risks, time and cost across a full IoT product cycle, and (3) it simplifies the connections between devices-to-devices and devices-to-applications.

7.3. SensorThings API Overview

The OGC SensorThings API data model consists of two parts: (1) the Sensing part and (2) the Tasking part. The Sensing part allows IoT devices and applications to CREATE, READ, UPDATE, and DELETE (i.e., HTTP POST, GET, PATCH, and DELETE) IoT data and metadata in a SensorThings service.

The Sensing part is designed based on the OGC/ISO Observation and Measurement (O&M) model [OGC 10-004r3 and ISO 19156:2011]. The key to the model is that an Observation is modeled as an act that produces a result whose value is an estimate of a property of the observation target or FeatureOfInterest. An Observation instance is classified by its event time (e.g., resultTime and phenonmenonTime), FeatureOfInterest, ObservedProperty, and the procedure used (often a Sensor). Moreover, Things are also modeled in the SensorThings API, and its definition follows the ITU-T definition: “an object of the physical world (physical things) or the information world (virtual things) that is capable of being identified and integrated into communication networks” [ITU-T Y.2060].

The geographical Locations of Things are useful in almost every application and as a result are included as well. For the Things whose location changed, the HistoricalLocations entities offer the history of the Thing’s locations. A Thing also can have multiple Datastreams. A Datastream is a collection of Observations grouped by the same ObservedProperty and Sensor. An Observation is an event performed by a Sensor that produces a result whose value is an estimate of an ObservedProperty of the FeatureOfInterest. Details of each above described entity are provided in Chapter 8.

7.4. SensorThings API and ISO/OGC Observations and Measurements

Managing and retrieving observations and metadata from IoT sensor systems is one of the most common use cases. As a result, SensorThings API’s sensing part is designed based on the O&M model. O&M defines models for the exchange of information describing observation acts, their results as well as the feature involved in sampling when making observations.

SensorThings API defines eight entities for the IoT sensing applications. base lists each component and its relationship with O&M. Low-cost and simple sensors are key enablers for the vision of IoT. As a result, SensorThings API uses the term of Sensor to describe the procedure that is used in making an Observation, instead of using O&M’s term of procedure.

Table 1. SensorThings API Sensing entities and equivalent concepts in O&M 2.0
SensorThings API Entities O&M 2.0 Concepts

Thing (and Locations, HistoricalLocations)

-

Datastream

-

Sensor

Procedure

Observation

Observation

ObservedProperty

Observed Property

FeatureOfInterest

Feature-Of-Interest

7.5. SensorThings API and OASIS OData

SensorThings API follows OData’s specification for requesting entities. That means the entity control information, resource path usages, query options, the relevant JSON encodings, and batch-processing request follow OData 4.0. By using OData’s standard ways for requesting entities, developers who are familiar with OData can create SensorThings applications easily. However, SensorThings API does not follow the OData Common Schema Definition Language and as a result does not follow its metadata service entity model. Thus, SensorThings API should not be seen as an OData compliant API. SensorThings API’s future work will explore possible harmonization between SensorThings API and OData.

7.6. SensorThings API and OGC Key-Value Pair (KVP) Encodings

Please note that SensorThings API’s Key-Value Pair (KVP) encoding is different from many existing OGC service implementation standards, such as SOS or Web Map Service (WMS). The main reason is that OData offers a complete set of KVP encodings (see Clause 9.3.3.6) that is designed specifically for RESTful web services, while OGC baseline currently does not have common KVP encodings for the RESTful binding. As a result, OGC SensorThings API version 1.1 chooses to use OData KVP encodings only. It is our future work to support OGC KVP encodings as an extension once a common OGC RESTful binding is available.

7.7. SensorThings API and Security

Things in the Internet of Things are connected to the network. Such ubiquitous network connectivity results in significant security threats. In the IoT reference model defined by ITU-T [ITU-T Y.2060] IoT security capabilities are not an independent layer but must be associated with all layers. The following figure shows the ITU-T IoT reference model. The reference model has four layers, namely (1) Applications Layer, (2) Service Support and Application Support Layer, (3) Network Layer, and (4) Device Layer. And security capabilities are a cross-layer component that is associated with the four layers.

Based on the IoT reference model, SensorThings API falls into the scope of the Service Support and Application Support Layer and the security issues should be addressed by the cross-cutting security capabilities. As a result, SensorThings API does not define specific security capabilities. Instead SensorThings API is designed to leverage the existing and future IoT security capabilities.

IoT Reference Model (adapted from [ITU-T Y.2060])
Figure 1. IoT Reference Model (adapted from [ITU-T Y.2060])

A service instance that implements security related extensions can notify clients of this by way of the serverSettings section of the document returned at the service root URI, as described in section Section 9.2.1. Security related extensions can also use this section to announce any security requirements to the clients.

8. The SensorThings API Sensing Entities

This chapter describes the SensorThings API data model. All data model requirements classes are grouped in the following requirements class:

Requirements Class

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel

Target Type

Web Service

Requirements class

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/entity-control-information

Requirements class

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/thing

Requirements class

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/location

Requirements class

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/historical-location

Requirements class

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/datastream

Requirements class

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/sensor

Requirements class

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/observed-property

Requirements class

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/observation

Requirements class

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/feature-of-interest

8.1. Common Control Information

Requirements Class

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/entity-control-information

Target Type

Web Service

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/entity-control-information/common-control-information

Each entity SHALL have the following common control information listed in Table 2.

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/entity-control-information/common-control-information

In SensorThings control information is represented as annotations whose names start with iot followed by a dot ( . ). Annotations are name/value pairs that have a dot ( . ) as part of the name.

When annotating a name/value pair for which the value is represented as a JSON object, each annotation is placed within the object and represented as a single name/value pair. In SensorThings the name always starts with the “at” sign (@), followed by the namespace iot, followed by a dot (.), followed by the name of the term (e.g., "@iot.id":1).

When annotating a name/value pair for which the value is represented as a JSON array or primitive value, each annotation that applies to this name/value pair is placed next to the annotated name/value pair and represented as a single name/value pair. The name is the same as the name of the name/value pair being annotated, followed by the “at” sign (@), followed by the namespace iot, followed by a dot (.), followed by the name of the term. (e.g., "Locations@iot.navigationLink":"http://example.org/v1.1/Things(1)/Locations")

Table 2. Common control information
Name Definition Data type Multiplicity and use

id

id is the system-generated identifier of an entity. id is unique among the entities of the same entity type in a SensorThings service.

Any

One (mandatory)

selfLink

selfLink is the absolute URL of an entity that is unique among all other entities.

URL

One (mandatory)

navigationLink

navigationLink is the relative or absolute URL that retrieves content of related entities.

URL

One-to-many
(mandatory)

8.2. The Sensing Entities

The SensorThings API Sensing part’s Entities are depicted in Figure 2.

Sensing Entities
Figure 2. Sensing Entities

In this section, we explain the properties in each entity type and the direct relation to the other entity types. In addition, for each entity type, we show an example of the associated JSON encoding.

8.2.1. Thing

Requirements Class

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/thing

Target Type

Web Service

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/thing/properties

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/thing/relations

Dependency

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/entity-control-information/common-control-information

The OGC SensorThings API follows the ITU-T definition, i.e., with regard to the Internet of Things, a thing is an object of the physical world (physical things) or the information world (virtual things) that is capable of being identified and integrated into communication networks [ITU-T Y.2060].

Each Thing entity SHALL have the mandatory properties and MAY have the optional properties listed in Table 3.

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/thing/properties
Table 3. Properties of a Thing entity
Name Definition Data type Multiplicity and use

name

A property provides a label for Thing entity, commonly a descriptive name.

CharacterString

One (mandatory)

description

This is a short description of the corresponding Thing entity.

CharacterString

One (mandatory)

properties

A JSON Object containing user-annotated properties as key-value pairs.

JSON Object

Zero-to-one

Each Thing entity SHALL have the direct relation between a Thing entity and other entity types listed in Table 4.

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/thing/relations
Table 4. Direct relation between a Thing entity and other entity types
Entity type Relation Description

Location

Many optional to many optional

The Location entity locates the Thing. Multiple Things MAY be located at the same Location. A Thing MAY not have a Location. A Thing SHOULD have only one Location.

However, in some complex use cases, a Thing MAY have more than one Location representations. In such case, the Thing MAY have more than one Locations. These Locations SHALL have different encodingTypes and the encodingTypes SHOULD be in different spaces (e.g., one encodingType in Geometrical space and one encodingType in Topological space).

HistoricalLocation

One mandatory to many optional

A Thing has zero-to-many HistoricalLocations. A HistoricalLocation has one-and-only-one Thing.

Datastream

One mandatory to many optional

A Thing MAY have zero-to-many Datastreams.
Example 1 an example of a Thing entity:
{
  "@iot.id": 1,
  "@iot.selfLink": "http://example.org/v1.1/Things(1)",
  "Locations@iot.navigationLink": "Things(1)/Locations",
  "Datastreams@iot.navigationLink": "Things(1)/Datastreams",
  "HistoricalLocations@iot.navigationLink": "Things(1)/HistoricalLocations",

  "name": "Oven",
  "description": "This thing is an oven.",
  "properties": {
    "owner": "Noah Liang",
    "color": "Black"
  }
}

8.2.2. Location

Requirements Class

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/location

Target Type

Web Service

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/location/properties

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/location/relations

Dependency

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/entity-control-information/common-control-information

The Location entity locates the Thing or the Things it associated with. A Thing’s Location entity is defined as the last known location of the Thing.

A Thing’s Location may be identical to the Thing’s Observations’ FeatureOfInterest. In the context of the IoT, the principle location of interest is usually associated with the location of the Thing, especially for in-situ sensing applications. For example, the location of interest of a wifi-connected thermostat should be the building or the room in which the smart thermostat is located. And the FeatureOfInterest of the Observations made by the thermostat (e.g., room temperature readings) should also be the building or the room. In this case, the content of the smart thermostat’s location should be the same as the content of the temperature readings’ feature of interest.

However, the ultimate location of interest of a Thing is not always the location of the Thing (e.g., in the case of remote sensing). In those use cases, the content of a Thing’s Location is different from the content of the FeatureOfInterest of the Thing’s Observations. Section 7.1.4 of [OGC 10-004r3 and ISO 19156:2011] provides a detailed explanation of observation location.

Each Location entity SHALL have the mandatory properties listed in Table 5.

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/location/properties
Table 5. Properties of a Location entity
Name Definition Data type Multiplicity and use

name

A property provides a label for Location entity, commonly a descriptive name.

CharacterString

One (mandatory)

description

The description about the Location.

CharacterString

One (mandatory)

encodingType

The encoding type of the Location property. Its value is one of the ValueCode enumeration (see Table 7).

ValueCode

One (mandatory)

location

The location type is defined by encodingType.

Any (i.e., the type is depending on the value of the encodingType)

One (mandatory)

properties

A JSON Object containing user-annotated properties as key-value pairs.

JSON Object

Zero-to-one

Each Location entity SHALL have the direct relation between a Location entity and other entity types listed in Table 6.

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/location/relations
Table 6. Direct relation between a Location entity and other entity types
Entity type Relation Description

Thing

Many optional to many optional

Multiple Things MAY locate at the same Location. A Thing MAY not have a Location.

HistoricalLocation

Many mandatory to many optional

A Location can have zero-to-many HistoricalLocations. One HistoricalLocation SHALL have one or many Locations.
Example 2 an example of a Location entity:
{
  "@iot.id": 1,
  "@iot.selfLink": "http://example.org/v1.1/Locations(1)",
  "Things@iot.navigationLink": "Locations(1)/Things",
  "HistoricalLocations@iot.navigationLink": "Locations(1)/HistoricalLocations",

  "name": "CCIT",
  "description": "Calgary Center for Innvative Technologies",
  "encodingType": "application/geo+json",
  "location": {
    "type": "Feature",
    "geometry":{
      "type": "Point",
      "coordinates": [-114.06,51.05]
    }
  }
}
Table 7. List of some code values used for identifying types for the encodingType of the Location and FeatureOfInterest entity
Location encodingType ValueCode Value

GeoJSON

application/geo+json

A thing can be geo-referenced in different spaces. For example, for some applications it is more suitable to use a topological space model (e.g., IndoorGML) to describe an indoor things’ location rather than using a geographic space model (e.g., GeoJSON). Currently GeoJSON is the only Location encodingType of the SensorThings API. In the future we expect to extend SensorThings API’s capabilities by adding additional encodingType to the code values listed in the above table. For example, one potential new Location encodingType can be a JSON encoding for IndoorGML.

8.2.3. HistoricalLocation

Requirements Class

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/historical-location

Target Type

Web Service

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/historical-location/properties

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/historical-location/relations

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/historical-location-auto-creation

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/historical-location-manual-creation

Dependency

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/entity-control-information/common-control-information

A Thing’s HistoricalLocation entity set provides the times of the current (i.e., last known) and previous locations of the Thing.

Each HistoricalLocation entity SHALL have the mandatory properties and MAY have the optional properties listed in Table 8.

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/historical-location/properties

Each HistoricalLocation entity SHALL have the direct relation between a HistoricalLocation entity and other entity types listed in Table 9.

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/historical-location/relations

When a Thing has a new Location, a new HistoricalLocation SHALL be created and added to the Thing automatically by the service. The current Location of the Thing SHALL only be added to this autogenerated HistoricalLocation automatically by the service, and SHALL not be created as HistoricalLocation directly by user.

http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/historical-location-auto-creation

The HistoricalLocation can also be created, updated and deleted. One use case is to migrate historical observation data from an existing observation data management system to a SensorThings API system. Another use case is to track the Location of a Thing, when a permanent network connection is not available. If the Location of a Thing is changed at a later time, when a network connection is available again, then the auto-generated Time of the HistoricalLocation entity would not reflect the time when the Thing was actually at the set Location, but only the time at which the change was sent to the server. To resolve this, the Location of a Thing can also be changed by adding a HistoricalLocation. If the time of a manually created HistoricalLocation is later than the time of all existing HistoricalLocations, then the Location of the Thing is updated to the Location of this manually created HistoricalLocation.

When a user directly adds new HistoricalLocation, and the time of this new HistoricalLocation is later than the latest HistoricalLocation for the Thing, then the Locations of the Thing are changed to the Locations of this new HistoricalLocation.

http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/historical-location-manual-creation
Table 8. Properties of a HistoricalLocation entity
Name Definition Data type Multiplicity and use

time

The time when the Thing is known at the Location.

TM_Instant (ISO-8601 Time String)

One (mandatory)
Table 9. Direct relation between an HistoricalLocation entity and other entity types
Entity type Relation Description

Location

Many optional to many mandatory

A Location can have zero-to-many HistoricalLocations. One HistoricalLocation SHALL have one or many Locations.

Thing

Many optional to one mandatory

A HistoricalLocation has one-and-only-one Thing. One Thing MAY have zero-to-many HistoricalLocations.
Example 3: An example of a HistoricalLocations entity set (e.g., Things(1)/HistoricalLocations)
{
  "value": [
    {
      "@iot.id": 1,
      "@iot.selfLink": "http://example.org/v1.1/HistoricalLocations(1)",
      "Locations@iot.navigationLink": "HistoricalLocations(1)/Locations",
      "Thing@iot.navigationLink": "HistoricalLocations(1)/Thing",
      "time": "2015-01-25T12:00:00-07:00"
    },
    {
      "@iot.id": 2,
      "@iot.selfLink": "http://example.org/v1.1/HistoricalLocations(2)",
      "Locations@iot.navigationLink": "HistoricalLocations(2)/Locations",
      "Thing@iot.navigationLink": "HistoricalLocations(2)/Thing",
      "time": "2015-01-25T13:00:00-07:00"
    }
  ],
  "@iot.nextLink":"http://example.org/v1.1/Things(1)/HistoricalLocations?$skip=2&$top=2"
}

8.2.4. Datastream

Requirements Class

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/datastream

Target Type

Web Service

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/datastream/properties

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/datastream/relations

Dependency

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/entity-control-information/common-control-information

Dependency

urn:iso:dis:iso:19156:clause:8.2.2

A Datastream groups a collection of Observations measuring the same ObservedProperty and produced by the same Sensor.

Each Datastream entity SHALL have the mandatory properties and MAY have the optional properties listed in Table 10.

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/datastream/properties

Each Datastream entity SHALL have the direct relation between a Datastream entity and other entity types listed in Table 11.

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/datastream/relations
Table 10. Properties of a Datastream entity
Name Definition Data type Multiplicity and use

name

A property provides a label for Datastream entity, commonly a descriptive name.

CharacterString

One (mandatory)

description

The description of the Datastream entity.

CharacterString

One (mandatory)

unitOfMeasurement

A JSON Object containing three key-value pairs. The name property presents the full name of the unitOfMeasurement; the symbol property shows the textual form of the unit symbol; and the definition contains the URI defining the unitOfMeasurement.

The values of these properties SHOULD follow the Unified Code for Unit of Measure (UCUM).

JSON Object

One (mandatory)

Note: When a Datastream does not have a unit of measurement (e.g., a OM_TruthObservation type), the corresponding unitOfMeasurement properties SHALL have null values.

observationType

The type of Observation (with unique result type), which is used by the service to encode observations.

ValueCode
see Table 12.

One (mandatory)

properties

A JSON Object containing user-annotated properties as key-value pairs.

JSON Object

Zero-to-one

observedArea

The spatial bounding box of the spatial extent of all FeaturesOfInterest that belong to the Observations associated with this Datastream.

GM_Envelope (GeoJSON Polygon)

Zero-to-one (optional)

phenomenonTime

The temporal interval of the phenomenon times of all observations belonging to this Datastream.

TM_Period (ISO 8601 Time Interval)

Zero-to-one (optional)

resultTime

The temporal interval of the result times of all observations belonging to this Datastream.

TM_Period (ISO 8601 Time Interval)

Zero-to-one (optional)
Table 11. Direct relation between a Datastream entity and other entity types
Entity type Relation Description

Thing

Many optional to one mandatory

A Thing has zero-to-many Datastreams. A Datastream entity SHALL only link to a Thing as a collection of Observations.

Sensor

Many optional to one mandatory

The Observations in a Datastream are performed by one-and-only-one Sensor. One Sensor MAY produce zero-to-many Observations in different Datastreams.

ObservedProperty

Many optional to one mandatory

The Observations of a Datastream SHALL observe the same ObservedProperty. The Observations of different Datastreams MAY observe the same ObservedProperty.

Observation

One mandatory to many optional

A Datastream has zero-to-many Observations. One Observation SHALL occur in one-and-only-one Datastream.
Example 4: A Datastream entity example
{
  "@iot.id": 1,
  "@iot.selfLink": "http://example.org/v1.1/Datastreams(1)",
  "Thing@iot.navigationLink": "HistoricalLocations(1)/Thing",
  "Sensor@iot.navigationLink": "Datastreams(1)/Sensor",
  "ObservedProperty@iot.navigationLink": "Datastreams(1)/ObservedProperty",
  "Observations@iot.navigationLink": "Datastreams(1)/Observations",

  "name": "oven temperature",
  "description": "This is a datastream measuring the air temperature in an oven.",
  "unitOfMeasurement": {
    "name": "degree Celsius",
    "symbol": "°C",
    "definition": "http://unitsofmeasure.org/ucum.html#para-30"
  },
  "observationType": "http://www.opengis.net/def/observationType/OGC-OM/2.0/OM_Measurement",
  "observedArea": {
    "type": "Polygon",
    "coordinates": [[[100,0],[101,0],[101,1],[100,1],[100,0]]]
  },
  "phenomenonTime": "2014-03-01T13:00:00Z/2015-05-11T15:30:00Z",
  "resultTime": "2014-03-01T13:00:00Z/2015-05-11T15:30:00Z"
}

The observationType defines the result types for specialized observations [OGC 10-004r3 and ISO 19156:2011 Table 3]. The following table shows some of the valueCodes that maps the UML classes in O&M v2.0 [OGC 10-004r3 and ISO 19156:2011] to observationType names and observation result types.

Table 12. List of some code values used for identifying types defined in the O&M conceptual model (OGC 10-004r3 and ISO 19156:2011 Clause 8.2.2)
O&M 2.0 Value Code Value (observationType names) Content of result

OM_CategoryObservation

http://www.opengis.net/def/observationType/OGC-OM/2.0/OM_CategoryObservation

URI

OM_CountObservation

http://www.opengis.net/def/observationType/OGC-OM/2.0/OM_CountObservation

integer

OM_Measurement

http://www.opengis.net/def/observationType/OGC-OM/2.0/OM_Measurement

double

OM_Observation

http://www.opengis.net/def/observationType/OGC-OM/2.0/OM_Observation

Any

OM_TruthObservation

http://www.opengis.net/def/observationType/OGC-OM/2.0/OM_TruthObservation

boolean

8.2.5. Sensor

Requirements Class

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/sensor

Target Type

Web Service

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/sensor/properties

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/sensor/relations

Dependency

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/entity-control-information/common-control-information

A Sensor is an instrument that observes a property or phenomenon with the goal of producing an estimate of the value of the property3.

Each Sensor entity SHALL have the mandatory properties and MAY have the optional properties listed in Table 13.

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/sensor/properties

Each Sensor entity SHALL have the direct relation between a Sensor entity and other entity types listed in Table 14.

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/sensor/relations
Table 13. Properties of a Sensor entity
Name Definition Data type Multiplicity and use

name

A property provides a label for Sensor entity, commonly a descriptive name.

CharacterString

One (mandatory)

description

The description of the Sensor entity.

CharacterString

One (mandatory)

encodingType

The encoding type of the metadata property. Its value is one of the ValueCode enumeration (see Table 15 for the available ValueCode).

ValueCode

One (mandatory)

metadata

The detailed description of the Sensor or system. The metadata type is defined by encodingType.

Any (depending on the value of the encodingType)

One (mandatory)

properties

A JSON Object containing user-annotated properties as key-value pairs.

JSON Object

Zero-to-one
Table 14. Direct relation between a Sensor entity and other entity types
Entity type Relation Description

Datastream

One mandatory to many optional

The Observations of a Datastream are measured with the same Sensor. One Sensor MAY produce zero-to-many Observations in different Datastreams.
Table 15. List of some code values used for identifying types for the encodingType of the Sensor entity
Sensor encodingType ValueCode Value

PDF

application/pdf

SensorML

http://www.opengis.net/doc/IS/SensorML/2.0

HTML

text/html

The Sensor encodingType allows clients to know how to interpret metadata’s value. Currently SensorThings API defines three common Sensor metadata encodingTypes. Most sensor manufacturers provide their sensor datasheets in a PDF format. As a result, PDF is a Sensor encodingType supported by SensorThings API. The second Sensor encodingType is SensorML. Lastly, some sensor datasheets are HTML documents rather than PDFs. Other encodingTypes are permitted (e.g., text/plain). Note that the metadata property may contain either a URL to metadata content (e.g., an https://, ftp://, etc. link to a PDF, SensorML, or HTML document) or the metadata content itself (in the case of text/plain or other encodingTypes that can be represented as valid JSON). It is up to clients to perform string parsing necessary to properly handle metadata content.

Example 5: An example of a Sensor entity
{
  "@iot.id": 1,
  "@iot.selfLink": "http://example.org/v1.1/Sensors(1)",
  "Datastreams@iot.navigationLink": "Sensors(1)/Datastreams",

  "name": "TMP36",
  "description": "TMP36 - Analog Temperature sensor",
  "encodingType": "application/pdf",
  "metadata": "http://example.org/TMP35_36_37.pdf"
}

8.2.6. ObservedProperty

Requirements Class

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/observed-property

Target Type

Web Service

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/observed-property/properties

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/observed-property/relations

Dependency

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/entity-control-information/common-control-information

An ObservedProperty specifies the phenomenon of an Observation.

Each ObservedProperty entity SHALL have the mandatory properties and MAY have the optional properties listed in Table 16.

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/observed-property/properties

Each ObservedProperty entity SHALL have the direct relation between a ObservedProperty entity and other entity types listed in Table 17.

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/observed-property/relations
Table 16. Properties of an ObservedProperty entity
Name Definition Data type Multiplicity and use

name

A property provides a label for ObservedProperty entity, commonly a descriptive name.

CharacterString

One (mandatory)

definition

The URI of the ObservedProperty. Dereferencing this URI SHOULD result in a representation of the definition of the ObservedProperty.

URI

One (mandatory)

description

A description about the ObservedProperty.

CharacterString

One (mandatory)

properties

A JSON Object containing user-annotated properties as key-value pairs.

JSON Object

Zero-to-one
Table 17. Direct relation between an ObservedProperty entity and other entity types
Entity type Relation Description

Datastream

One mandatory to many optional

The Observations of a Datastream observe the same ObservedProperty. The Observations of different Datastreams MAY observe the same ObservedProperty.
Example 6: an example ObservedProperty entity
{
  "@iot.id": 1,
  "@iot.selfLink": "http://example.org/v1.1/ObservedProperties(1)",
  "Datastreams@iot.navigationLink": "ObservedProperties(1)/Datastreams",
  "description": "The dewpoint temperature is the temperature to which the
                  air must be cooled, at constant pressure, for dew to form.
                  As the grass and other objects near the ground cool to
                  the dewpoint, some of the water vapor in the atmosphere
                  condenses into liquid water on the objects.",
  "name": "DewPoint Temperature",
  "definition": "http://dbpedia.org/page/Dew_point"
}

8.2.7. Observation

Requirements Class

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/observation

Target Type

Web Service

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/observation/properties

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/observation/relations

Dependency

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/entity-control-information/common-control-information

Dependency

urn:iso:dis:iso:19156:clause:7.2.2

An Observation is the act of measuring or otherwise determining the value of a property [OGC 10-004r3 and ISO 19156:2011]

Each Observation entity SHALL have the mandatory properties and MAY have the optional properties listed in Table 18.

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/observation/properties

Each Observation entity SHALL have the direct relation between an Observation entity and other entity types listed in Table 19.

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/observation/relations
Table 18. Properties of an Observation entity
Name Definition Data type Multiplicity and use

phenomenonTime

The time instant or period of when the Observation happens.

Note: Many resource-constrained sensing devices do not have a clock. As a result, a client may omit phenonmenonTime when POST new Observations, even though phenonmenonTime is a mandatory property. When a SensorThings service receives a POST Observations without phenonmenonTime, the service SHALL assign the current server time to the value of the phenomenonTime.

TM_Object (ISO 8601 Time string or Time Interval string (e.g., 2010-12-23T10:20:00.00-07:00 or 2010-12-23T10:20:00.00-07:00/2010-12-23T12:20:00.00-07:00))

One (mandatory)

result

The estimated value of an ObservedProperty from the Observation.

Any (depends on the observationType defined in the associated Datastream)

One (mandatory)

resultTime

The time of the Observation’s result was generated.

Note: Many resource-constrained sensing devices do not have a clock. As a result, a client may omit resultTime when POST new Observations, even though resultTime is a mandatory property. When a SensorThings service receives a POST Observations without resultTime, the service SHALL assign a null value to the resultTime.

TM_Instant (ISO 8601 Time string)

One (mandatory)

resultQuality

Describes the quality of the result.

DQ_Element

Zero-to-many

validTime

The time period during which the result may be used.

TM_Period (ISO 8601 Time Interval string)

Zero-to-one

parameters

Key-value pairs showing the environmental conditions during measurement.

JSON Object

Zero-to-One
Table 19. Direct relation between an Observation entity and other entity types
Entity type Relation Description

Datastream

Many optional to one mandatory

A Datastream can have zero-to-many Observations. One Observation SHALL occur in one-and-only-one Datastream.

FeatureOfInterest

Many optional to one mandatory

An Observation observes on one-and-only-one FeatureOfInterest. One FeatureOfInterest could be observed by zero-to-many Observations.
Example 7 An Observation entity example - The following example shows an Observation whose Datastream has an ObservationType of OM_Measurement. A result’s data type is defined by the observationType.
{
  "@iot.id": 1,
  "@iot.selfLink": "http://example.org/v1.1/Observations(1)",
  "FeatureOfInterest@iot.navigationLink": "Observations(1)/FeatureOfInterest",
  "Datastream@iot.navigationLink":"Observations(1)/Datastream",

  "phenomenonTime": "2014-12-31T11:59:59.00+08:00",
  "resultTime": "2014-12-31T11:59:59.00+08:00",
  "result": 70.4
}

8.2.8. FeatureOfInterest

Requirements Class

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/feature-of-interest

Target Type

Web Service

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/feature-of-interest/properties

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/feature-of-interest/relations

Dependency

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/entity-control-information/common-control-information

An Observation results in a value being assigned to a phenomenon. The phenomenon is a property of a feature, the latter being the FeatureOfInterest of the Observation [OGC and ISO 19156:2011]. In the context of the Internet of Things, many Observations’ FeatureOfInterest can be the Location of the Thing. For example, the FeatureOfInterest of a wifi-connect thermostat can be the Location of the thermostat (i.e., the living room where the thermostat is located in). In the case of remote sensing, the FeatureOfInterest can be the geographical area or volume that is being sensed.

Each FeatureOfInterest entity SHALL have the mandatory properties listed in Table 20.

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/feature-of-interest/properties

Each FeatureOfInterest entity SHALL have the direct relation between a FeatureOfInterest entity and other entity types listed in Table 21.

http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/feature-of-interest/relations
Table 20. Properties of a FeatureOfInterest entity
Name Definition Data type Multiplicity and use

name

A property provides a label for FeatureOfInterest entity, commonly a descriptive name.

CharacterString

One (mandatory)

description

The description about the FeatureOfInterest.

CharacterString

One (mandatory)

encodingType

The encoding type of the feature property.

Its value is one of the ValueCode enumeration (see Table 7 for the available ValueCode).

ValueCode

One (mandatory)

feature

The detailed description of the feature. The data type is defined by encodingType.

Any

One (mandatory)

properties

A JSON Object containing user-annotated properties as key-value pairs.

JSON Object

Zero-to-one
Table 21. Direct relation between a FeatureOfInterest entity and other entity types
Entity type Relation Description

Observation

One mandatory to many optional

An Observation observes on one-and-only-one FeatureOfInterest. One FeatureOfInterest could be observed by zero-to-many Observations.
Example 8: an example of a FeatureOfInterest entity
{
  "@iot.id": 1,
  "@iot.selfLink": "http://example.org/v1.1/FeaturesOfInterest(1)",
  "Observations@iot.navigationLink": "FeaturesOfInterest(1)/Observations",

  "name": "Weather Station YYC.",
  "description": "This is a weather station located at the Calgary Airport.",
  "encodingType": "application/geo+json",
  "feature": {
    "type": "Feature",
    "geometry":{
      "type": "Point",
      "coordinates": [-114.06,51.05]
    }
  }
}

9. SensorThings Service Interface

An OGC SensorThings API service exposes a service document resources that describe its data model. The service document lists the entity sets that can be CRUD. SensorThings API clients can use the service document to navigate the available entities in a hypermedia-driven fashion.

9.1. URI Components

The OGC SensorThings API service groups the same types of entities into entity sets.Each entity has a unique identifier and one-to-many properties. Also, in the case of an entity holding a relationship with entities in other entity sets, this type of relationship is expressed with navigation properties (i.e., navigationLink and associationLink).

Therefore, in order to perform CRUD actions on the resources, the first step is to address to the target resource(s) through URI. There are three major URI components used here, namely (1) the service root URI, (2) the resource path, and (3) the query options. In addition, the service root URI consists of two parts: (1) the location of the SensorThings service and (2) the version number. The version number follows the format indicated below:

"v"majorversionnumber + "." + minorversionnumber

Example 9: complete URI example

http://example.org/v1.1/Observations?$orderby=ID&$top=10
_______________________/___________/___________________/
          |                 |               |
  service root URI     resource path   query options

By attaching the resource path after the service root URI, clients can address to different types of resources such as an entity set, an entity, a property, or a navigation property. Finally, clients can apply query options after the resource path to further process the addressed resources, such as sorting by properties or filtering with criteria.

9.2. Resource Path

Requirements Class

http://www.opengis.net/spec/iot_sensing/1.1/req/resource-path

Target Type

Web Service

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/resource-path/resource-path-to-entities

Dependency

The resource path comes right after the service root URI and can be used to address to different resources. The following lists the usages of the resource path.

An OGC SensorThings API service SHALL support all the resource path usages listed in Section 9.2.

http://www.opengis.net/spec/iot_sensing/1.1/req/resource-path/resource-path-to-entities

9.2.1. Usage 1: no resource path

URI Pattern: SERVICE_ROOT_URI

Response: A JSON object with a property named value and a property named serverSettings. The value of the property named value SHALL be a JSON Array containing one element for each entity set of the SensorThings Service. The value of the property named serverSettings SHALL be a JSON Object describing the features the server supports that can not easily be detected by querying the service.

Each element of the value array SHALL be a JSON object with at least two name/value pairs, one with name name containing the name of the entity set (e.g., Things, Locations, Datastreams, Observations, ObservedProperties and Sensors) and one with name url containing the URL of the entity set, which may be an absolute or a relative URL.
[Adapted from OData 4.0-JSON-Format section 5]

The serverSettings object SHALL contain the property conformance of the type Array, containing the URIs of all requirements from this specification and any extensions that the service implements. If a service implements all requirements from a requirements class, it only needs to list the requirements class id.

Security extensions can modify the list of requirements to only show those requirements that the user is allowed to use. For example, if a user is not allowed to delete entities, the security extension can hide the create-update-delete/delete-entity requirement. In the most extreme case, a security extension would hide all requirements for a user that is not authenticated, except its own requirement and the instructions on how to authenticate.

Extensions that need to expose additional server settings may do so in a property of the serverSettings object that is named after the conformance class URI of the requirement that defines this setting.

Example 10: a SensorThings request with no resource path

Example Request:
http://example.org/v1.1/
Example Response:
{
 "serverSettings": {
    "conformance": [
        "http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel",
        "http://www.opengis.net/spec/iot_sensing/1.1/req/resource-path/resource-path-to-entities",
        "http://www.opengis.net/spec/iot_sensing/1.1/req/request-data",
        "http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/create-entity",
        "http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/link-to-existing-entities",
        "http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/deep-insert",
        "http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/deep-insert-status-code",
        "http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/update-entity",
        "http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/delete-entity",
        "http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/historical-location-auto-creation",
        "http://www.opengis.net/spec/iot_sensing/1.1/req/create-observations-via-mqtt/observations-creation",
        "http://www.opengis.net/spec/iot_sensing/1.1/req/receive-updates-via-mqtt/receive-updates"
    ],
    "http://www.opengis.net/spec/iot_sensing/1.1/req/receive-updates-via-mqtt/receive-updates": {
      "endpoints": [
        "mqtt://server.example.com:1833",
        "ws://server.example.com/sensorThings",
      ]
    },
    "http://www.opengis.net/spec/iot_sensing/1.1/req/create-observations-via-mqtt/observations-creation": {
      "endpoints": [
        "mqtts://server.example.com:8883",
        "wss://server.example.com:443/sensorThings"
      ]
    }
  },
  "value": [
    {
      "name": "Things",
      "url": "http://example.org/v1.1/Things"
    },
    {
      "name": "Locations",
      "url": "http://example.org/v1.1/Locations"
    },
    {
      "name": "Datastreams",
      "url": "http://example.org/v1.1/Datastreams"
    },
    {
      "name": "Sensors",
      "url": "http://example.org/v1.1/Sensors"
    },
    {
      "name": "Observations",
      "url": "http://example.org/v1.1/Observations"
    },
    {
      "name": "ObservedProperties",
      "url": "http://example.org/v1.1/ObservedProperties"
    },
    {
      "name": "FeaturesOfInterest",
      "url": "http://example.org/v1.1/FeaturesOfInterest"
    }
  ]
}

9.2.2. Usage 2: address to a collection of entities

To address to an entity set, users can simply put the entity set name after the service root URI. The service returns a JSON object with a property of value. The value of the property SHALL be a list of the entities in the specified entity set.

URI Pattern: SERVICE_ROOT_URI/ENTITY_SET_NAME

Response: A list of all entities (with all the properties) in the specified entity set when there is no service-driven pagination imposed. The response is represented as a JSON object containing a name/value pair named value. The value of the value name/value pair is a JSON array where each element is representation of an entity or a representation of an entity reference. An empty collection is represented as an empty JSON array.

The count annotation represents the number of entities in the collection. If present, it comes before the value name/value pair.

When there is service-driven pagination imposed, the nextLink annotation is included in a response that represents a partial result.

[Adapted from OData 4.0-JSON-Format section 12]

Example 11 an example to address an entity set

Example Request:
http://example.org/v1.1/ObservedProperties
Example Response:
{
  "@iot.count":84,
  "value": [
    {
      "@iot.id": 1,
      "@iot.selfLink": "http://example.org/v1.1/ObservedProperties(1)",
      "Datastreams@iot.navigationLink": "ObservedProperties(1)/Datastreams",
      "description": "The dew point is the temperature at which the water
                      vapor in air at constant barometric pressure condenses
                      into liquid water at the same rate at which it evaporates.",
      "name": "DewPoint Temperature",
      "definition": "http://dbpedia.org/page/Dew_point"
    },
    {
      "@iot.id ": 2,
      "@iot.selfLink": "http://example.org/v1.1/ObservedProperties(2)",
      "Datastreams@iot.navigationLink": "ObservedProperties(2)/Datastreams",
      "description": "Relative humidity is the ratio of the partial pressure
                      of water vapor in an air-water mixture to the saturated
                      vapor pressure of water at a prescribed temperature.",
      "name": "Relative Humidity",
      "definition": "http://dbpedia.org/page/Relative_humidity"
    },{…},{…},{…}
  ],
  "@iot.nextLink":"http://example.org/v1.1/ObservedProperties?$top=5&$skip=5"
}

9.2.3. Usage 3: address to an entity in a collection

Users can address to a specific entity in an entity set by place the unique identifier of the entity between brace symbol “()” and put after the entity set name. The service then returns the entity with all its properties.

URI Pattern: SERVICE_ROOT_URI/ENTITY_SET_NAME(ID_OF_THE_ENTITY)

Response: A JSON object of the entity (with all its properties) that holds the specified id in the entity set.

Example 12: an example request that addresses to an entity in a collection

Example Request:
http://example.org/v1.1/Things(1)

9.2.4. Usage 4: address to a property of an entity

Users can address to a property of an entity by specifying the property name after the URI addressing to the entity. The service then returns the value of the specified property. If the property has a complex type value, properties of that value can be addressed by further property name composition.

If the property is single-valued and has the null value, the service SHALL respond with 204 No Content. If the property is not available, for example due to permissions, the service SHALL respond with 404 Not Found.

[Adapted from OData 4.0-Protocol 11.2.3]

URI Pattern: SERVICE_ROOT_URI/RESOURCE_PATH_TO_AN_ENTITY/PROPERTY_NAME

Response: The specified property of an entity that holds the id in the entity set.

Example 13: an example to address to a property of an entity

Example Request:
http://example.org/v1.1/Observations(1)/resultTime
Example Response:
{
  "resultTime": "2010-12-23T10:20:00-07:00"
}

9.2.5. Usage 5: address to the value of an entity’s property

To address the raw value of a primitive property, clients append a path segment containing the string $value to the property URL.

The default format for TM_Object types is text/plain using the ISO8601 format, such as 2014-03-01T13:00:00Z/2015-05-11T15:30:00Z for TM_Period and 2014-03-01T13:00:00Z for TM_Instant.

URI Pattern: SERVICE_ROOT_URI/ENTITY_SET_NAME(ID_OF_THE_ENTITY)/PROPERTY_NAME/$value

Response: The raw value of the specified property of an entity that holds the id in the entity set.

Example 14: an example of addressing to the value of an entity’s property

Example:

http://example.org/v1.1/Observations(1)/resultTime/$value
Example Response:
  2015-01-12T23:00:13-07:00

9.2.6. Usage 6: address to a navigation property (navigationLink)

As the entities in different entity sets may hold some relationships, users can request the linked entities by addressing to a navigation property of an entity. The service then returns one or many entities that hold a certain relationship with the specified entity.

URI Pattern: SERVICE_ROOT_URI/ENTITY_SET_NAME(ID_OF_THE_ENTITY)/LINK_NAME

Response: A JSON object of one entity or a JSON array of many entities that holds a certain relationship with the specified entity.

Example 15: an example request addressing to a navigational property

http://example.org/v1.1/Datastreams(1)/Observations
returns all the Observations in the Datastream that holds the id 1.

As the entities in different entity sets may hold some relationships, users can request the linked entities’ selfLinks by addressing to an association link of an entity. An associationLink can be used to retrieve a reference to an entity or an entity set related to the current entity. Only the selfLinks of related entities are returned when resolving associationLinks.

URI Pattern: SERVICE_ROOT_URI/ENTITY_SET_NAME(KEY_OF_THE_ENTITY)/LINK_NAME/$ref

Response: A JSON object with a value property. The value of the value property is a JSON array containing one element for each associationLink. Each element is a JSON object with a name/value pairs. The name is @iot.selfLink and the value is the selfLink of the related entity.

Example 16: an example of addressing to an association link

Example Request:
http://example.org/v1.1/Datastreams(1)/Observations/$ref

returns all the selfLinks of the Observations of Datastream(1).

Example Response:
{
  "value": [
    {
      "@iot.selfLink": "http://example.org/v1.1/Observations(1)"
    },
    {
      "@iot.selfLink": "http://example.org/v1.1/Observations(2)"
    }
  ]
}

9.2.8. Usage 8: nested resource path

As users can use navigation properties to link from one entity set to another, users can further extend the resource path with unique identifiers, properties, or links (i.e., Usage 3, 4 and 6).

Example 17: examples of nested resource path

Example Request 1:

http://example.org/v1.1/Datastreams(1)/Observations(1)

returns a specific Observation entity in the Datastream.

Example Request 2:

http://example.org/v1.1/Datastreams(1)/Observations(1)/resultTime

turns the resultTime property of the specified Observation in the Datastream.

Example Request 3:

http://example.org/v1.1/Datastreams(1)/Observations(1)/FeatureOfInterest

returns the FeatureOfInterest entity of the specified Observation in the Datastream.

9.3. Requesting Data

Requirements Class

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data

Target Type

Web Service

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/order

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/expand

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/select

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/status-code

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/query-status-code

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/orderby

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/top

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/skip

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/pagination

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/count

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/filter

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/built-in-filter-operations

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/built-in-query-functions

Dependency

http://docs.oasis-open.org/odata/odata/v4.0/errata02/os/complete/part1-protocol/odata-v4.0-errata02-os-part1-protocol-complete.html#_Toc406398292

Dependency

http://docs.oasis-open.org/odata/odata/v4.0/errata02/os/complete/part1-protocol/odata-v4.0-errata02-os-part1-protocol-complete.html#_Toc406398297

Dependency

http://docs.oasis-open.org/odata/odata/v4.0/errata02/os/complete/part1-protocol/odata-v4.0-errata02-os-part1-protocol-complete.html#_Toc406398299

Dependency

http://docs.oasis-open.org/odata/odata/v4.0/errata02/os/complete/part1-protocol/odata-v4.0-errata02-os-part1-protocol-complete.html#_Toc406398300

Clients issue HTTP GET requests to OGC SensorThings API services for data. The resource path of the URL specifies the target of the request. Additional query operators can be specified through query options that are presented as follows. The query operators are prefixed with a dollar ($) character and specified as key-value pairs after the question symbol (?) in the request URI. Many of the OGC SensorThings API’s query options are adapted from OData’s query options. OData developers should be able to pick up SensorThings API query options very quickly.

OGC SensorThings API services are hypermedia driven services that return URLs to the client. If a client subsequently requests the advertised resource and the URL has expired, then the service SHALL respond with 410 Gone. If this is not feasible, the service SHALL respond with 404 Not Found.

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/status-code

If a service does not support a system query option, it SHALL fail any request that contains the unsupported option and SHALL return 501 Not Implemented.

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/query-status-code

9.3.1. Evaluating System Query Options

An OGC SensorThings API service SHALL evaluate the system query options following the order specified in Section 9.3.1.

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/order

The OGC SensorThings API adapts many of OData’s system query options and their usage. These query options allow refining the request.

The result of the service request is as if the system query options were evaluated in the following order.

Prior to applying any server-driven pagination:

  • $filter

  • $count

  • $orderby

  • $skip

  • $top

After applying any server-driven pagination:

  • $select

  • $expand

9.3.2. Specifying Properties to Return

The $select and $expand system query options enable the client to specify the set of properties to be included in a response.

9.3.2.1. $expand

The $expand system query option indicates the related entities to be represented inline. The value of the $expand query option SHALL be a comma separated list of navigation property names. Additionally, each navigation property can be followed by a forward slash and another navigation property to enable identifying a multi-level relationship.

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/expand

Example 18: examples of $expand query option

Example Request 1:

http://example.org/v1.1/Things?$expand=Datastreams

returns the entity set of Things as well as each of the Datastreams associated with each Thing entity.

Example Request 1 Response:

{
  "values": [
    {
      "@iot.id": 1,
      "@iot.selfLink": "http://example.org/v1.1/Things(1)",
      "Locations@iot.navigationLink": "Things(1)/Locations",
      "Datastreams@iot.count":1,
      "Datastreams": [
        {
          "@iot.id": 1,
          "@iot.selfLink": "http://example.org/v1.1/Datastreams(1)",
          "name": "oven temperature",
          "description": "This is a datastream measuring the air temperature in an oven.",
          "unitOfMeasurement": {
            "name": "degree Celsius",
            "symbol": "°C",
            "definition": "http://unitsofmeasure.org/ucum.html#para-30"
          },
          "observationType": "http://www.opengis.net/def/observationType/OGC-OM/2.0/OM_Measurement",
          "observedArea": {
            "type": "Polygon",
            "coordinates": [[[100,0],[101,0],[101,1],[100,1],[100,0]]]
          },
          "phenomenonTime": "2014-03-01T13:00:00Z/2015-05-11T15:30:00Z",
          "resultTime": "2014-03-01T13:00:00Z/2015-05-11T15:30:00Z"
        }
      ],
      "HistoricalLocations@iot.navigationLink": "Things(1)/HistoricalLocations",
      "description": "This thing is a convection oven.",
      "name": "Oven",
      "properties": {
        "owner": "John Doe",
        "color": "Silver"
      }
    }
  ]
}

Example Request 2:

http://example.org/v1.1/Things?$expand=Datastreams/ObservedProperty

returns the collection of Things, the Datastreams associated with each Thing, and the ObservedProperty associated with each Datastream.

Example Request 3:

http://example.org/v1.1/Datastreams(1)?$expand=Observations,ObservedProperty

returns the Datastream whose id is 1 as well as the Observations and ObservedProperty associated with this Datastream.

Query options can be applied to the expanded navigation property by appending a semicolon-separated list of query options, enclosed in parentheses, to the navigation property name. Allowed system query options are $filter, $select, $orderby, $skip, $top, $count, and $expand.

[Adapted from OData 4.0- URL 5.1.2]

Example Request 4:

http://example.org/v1.1/Datastreams(1)?$expand=Observations($filter=result eq 1)

returns the Datastream whose id is 1 as well as its Observations with a result equal to 1.

9.3.2.2. $select

The $select system query option requests the service to return only the properties explicitly requested by the client. The value of a $select query option SHALL be a comma-separated list of selection clauses. Each selection clause SHALL be a property name (including navigation property names). In the response, the service SHALL return the specified content, if available, along with any available expanded navigation properties.

[Adapted from OData 4.0-Protocol 11.2.4.1]

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/select

Example 19: examples of $select query option

Example Request 1:

http://example.org/v1.1/Observations?$select=result,resultTime

returns only the result and resultTime properties for each Observation entity.

Example Request 2:

http://example.org/v1.1/Datastreams(1)?$select=id&$expand=Observations/FeatureOfInterest

returns the id property of the Datastream entity, and all the properties of the entity identified by the Observations and FeatureOfInterest navigation properties (Expanded items are implicitly selected).

Example Request 3:

http://example.org/v1.1/Datastreams(1)?$expand=Observations($select=result)

returns the Datastream whose id is 1 as well as the result property of the entity identified by the Observations navigation property.

9.3.3. Query Entity Sets

9.3.3.1. $orderby

The $orderby system query option specifies the order in which items are returned from the service. The value of the $orderby system query option SHALL contain a comma-separated list of expressions whose primitive result values are used to sort the items. A special case of such an expression is a property path terminating on a primitive property.

The expression MAY include the suffix asc for ascending or desc for descending, separated from the property name by one or more spaces. If asc or desc is not specified, the service SHALL order by the specified property in ascending order.

Null values SHALL come before non-null values when sorting in ascending order and after non-null values when sorting in descending order.

Items SHALL be sorted by the result values of the first expression, and then items with the same value for the first expression SHALL be sorted by the result value of the second expression, and so on.

[Note: Adapted from OData 4.0-Protocol 11.2.5.2]

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/orderby

Example 20: examples of $orderby query option

Example Request 1:

http://example.org/v1.1/Observations?$orderby=result

returns all Observations ordered by the result property in ascending order.

Example Request 2:

http://example.org/v1.1/Observations?$expand=Datastream&$orderby=Datastreams/id desc, phenomenonTime

returns all Observations ordered by the id property of the linked Datastream entry in descending order, then by the phenomenonTime property of Observations in ascending order.

9.3.3.2. $top

The $top system query option specifies the limit on the number of items returned from a collection of entities. The value of the $top system query option SHALL be a non-negative integer n. The service SHALL return the number of available items up to but not greater than the specified value n.

If no unique ordering is imposed through an $orderby query option, the service SHALL impose a stable ordering across requests that include $top.

[Note: Adapted from OData 4.0-Protocol 11.2.5.3]

In addition, if the $top value exceeds the service-driven pagination limitation (i.e., the largest number of entities the service can return in a single response), the $top query option SHALL be discarded and the server-side pagination limitation SHALL be imposed.

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/top

Example 21: examples of $top query option

Example Request 1:

http://example.org/v1.1/Things?$top=5

returns only the first five entities in the Things collection.

Example Request 2:

http://example.org/v1.1/Observations?$top=5&$orderby=phenomenonTime%20desc

returns the first five Observation entries after sorted by the phenomenonTime property in descending order.

9.3.3.3. $skip

The $skip system query option specifies the number for the items of the queried collection that SHALL be excluded from the result. The value of $skip system query option SHALL be a non-negative integer n. The service SHALL return items starting at position n+1.

Where $top and $skip are used together, $skip SHALL be applied before $top, regardless of the order in which they appear in the request.

If no unique ordering is imposed through an $orderby query option, the service SHALL impose a stable ordering across requests that include $skip.

[Note: Adapted from OData 4.0-Protocol 11.2.5.4]

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/skip

Example 22: examples of $skip query option

Example Request 1:

http://example.org/v1.1/Things?$skip=5

returns Thing entities starting with the sixth Thing entity in the Things collection.

Example Request 2:

http://example.org/v1.1/Observations?$skip=2&$top=2&$orderby=resultTime

returns the third and fourth Observation entities from the collection of all Observation entities when the collection is sorted by the resultTime property in ascending order.

9.3.3.4. $count

The $count system query option with a value of true specifies that the total count of items within a collection matching the request SHALL be returned along with the result. A $count query option with a value of false (or not specified) hints that the service SHALL not return a count.

The service SHALL return an HTTP Status code of 400 Bad Request if a value other than true or false is specified.

The $count system query option SHALL ignore any $top, $skip, or $expand query options, and SHALL return the total count of results across all pages including only those results matching any specified $filter. Clients should be aware that the count returned inline may not exactly equal the actual number of items returned, due to latency between calculating the count and enumerating the last value or due to inexact calculations on the service.

[Adapted from OData 4.0-Protocol 11.2.5.5]

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/count

Example 23: examples of $count query option

Example Request 1:

http://example.org/v1.1/Things?$count=true

returns, along with the results, the total number of Things in the collection.

Example Response:
{
  "@iot.count": 2,
  "value": [
    {…},
    {…}
  ]
}
9.3.3.5. $filter

The $filter system query option allows clients to filter a collection of entities that are addressed by a request URL. The expression specified with $filter is evaluated for each entity in the collection, and only items where the expression evaluates to true SHALL be included in the response. Entities for which the expression evaluates to false or to null, or which reference properties that are unavailable due to permissions, SHALL be omitted from the response.

[Adapted from Data 4.0-URL Conventions 5.1.1]

The expression language that is used in $filter operators SHALL support references to properties and literals. The literal values SHALL be strings enclosed in single quotes, numbers and boolean values (true or false) or datetime values represented as ISO 8601 time string.

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/filter

Example 24: examples of $filter query option

Example Request 1:

http://example.org/v1.1/Observations?$filter=result lt 10.00

returns all Observations whose result is less than 10.00.

In addition, clients can choose to use the properties of linked entities in the $filter predicate. The following are examples of the possible uses of the $filter in the data model of the SensorThings service.

Example Request 2:

http://example.org/v1.1/Observations?$filter=Datastream/id eq 1

returns all Observations whose Datastream’s id is 1.

Example Request 3:

http://example.org/v1.1/Things?$filter=geo.distance(Locations/location, geography'POINT(-122 43)') gt 1

returns Things that the distance between their last known locations and POINT(-122 43) is greater than 1.

Example Request 4:

http://example.org/v1.1/Things?$expand=Datastreams/Observations/FeatureOfInterest&$filter=Datastreams/Observations/FeatureOfInterest/id eq ‘FOI_1’ and Datastreams/Observations/resultTime ge 2010-06-01T00:00:00Z and Datastreams/Observations/resultTime le 2010-07-01T00:00:00Z

returns Things that have any observations of a feature of interest with a unique identifier equals to ’FOI_1’ in June 2010.

9.3.3.5.1. Built-in filter operations

The OGC SensorThings API supports a set of built-in filter operations, as described in the following table. These built-in filter operator usages and definitions follow the [OData Specification Section 11.2.5.1.1] and [OData Version 4.0 ABNF]. The operator precedence is described in [OData Version 4.0 Part 2: URL Conventions Section 5.1.1.8].

The built-in filter operators SHALL be as defined in Table 22.

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/built-in-filter-operations
Table 22. Built-in Filter Operators
Operator Description Example

Comparison Operators

eq

Equal

/Datastreams?$filter=unitOfMeasurement/name eq 'degree Celsius'

ne

Not equal

/Datastreams?$filter=unitOfMeasurement/name ne 'degree Celsius'

gt

Greater than

/Observations?$filter=result gt 20.0

ge

Greater than or equal

/Observations?$filter=result ge 20.0

lt

Less than

/Observations?$filter=result lt 100

le

Less than or equal

/Observations?$filter=result le 100

Logical Operators

and

Logical and

/Observations?$filter=result le 3.5 and FeatureOfInterest/id eq 1

or

Logical or

/Observations?$filter=result gt 20 or result le 3.5

not

Logical negation

/Things?$filter=not startswith(description,'test')

Arithmetic Operators

add

Addition

/Observations?$filter=result add 5 gt 10

sub

Subtraction

/Observations?$filter=result sub 5 gt 10

mul

Multiplication

/Observations?$filter=result mul 2 gt 2000

div

Division

/Observations?$filter=result div 2 gt 4

mod

Modulo

/Observations?$filter=result mod 2 eq 0

Grouping Operators

( )

Precedence grouping

/Observations?$filter=(result sub 5) gt 10
9.3.3.5.2. Built-in query functions

The OGC SensorThings API supports a set of functions that can be used with the $filter or $orderby query operations. The following table lists the available functions and they follows the OData Canonical function definitions listed in Section 5.1.1.4 of the [OData Version 4.0 Part 2: URL Conventions] and the syntax rules for these functions are defined in [OData Version 4.0 ABNF].

In order to support spatial relationship functions, SensorThings API defines nine additional geospatial functions based on the spatial relationship between two geometry objects. The spatial relationship functions are defined in the OGC Simple Feature Access specification [OGC 06-104r4 part 1, clause 6.1.2.3]. The names of these nine functions start with a prefix st_ following the OGC Simple Feature Access specification [OGC 06-104r4]. In addition, the Well-Known Text (WKT) format is the default input geometry for these nine functions.

The built-in query functions SHALL be as defined in Table 23.

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/built-in-query-functions
Table 23. Built-in Query Functions
Function Example

String Functions

bool substringof(string p0, string p1)

substringof('Sensor Things',description)

bool endswith(string p0, string p1)

endswith(description,'Things')

bool startswith(string p0, string p1)

startswith(description,'Sensor')

int length(string p0)

length(description) eq 13

int indexof(string p0, string p1)

indexof(description,'Sensor') eq 1

string substring(string p0, int p1)
string substring(string p0, int p1, int p2)

substring(description,1) eq 'ensor Things'
substring(description,2,4) eq 'nsor'

string tolower(string p0)

tolower(description) eq 'sensor things'

string toupper(string p0)

toupper(description) eq 'SENSOR THINGS'

string trim(string p0)

trim(description) eq 'Sensor Things'

string concat(string p0, string p1)

concat(concat(unitOfMeasurement/symbol,', '), unitOfMeasurement/name) eq 'degree, Celsius'

Date Functions

int year

year(resultTime) eq 2015

int month

month(resultTime) eq 12

int day

day(resultTime) eq 8

int hour

hour(resultTime) eq 1

int minute

minute(resultTime) eq 0

int second

second(resultTime) eq 0

int fractionalseconds

second(resultTime) eq 0

int date

date(resultTime) ne date(validTime)

time

time(resultTime) le validTime

int totaloffsetminutes

totaloffsetminutes(resultTime) eq 60

now

resultTime ge now()

mindatetime

resultTime eq mindatetime()

maxdatetime

resultTime eq maxdatetime()

Math Functions

round

round(result) eq 32

floor

floor(result) eq 32

ceiling

ceiling(result) eq 33

Geospatial Functions

double geo.distance(Point p0, Point p1)

geo.distance(location, geography'POINT (30 10)')

double geo.length(LineString p0)

geo.length(geography'LINESTRING (30 10, 10 30, 40 40)')

bool geo.intersects(Point p0, Polygon p1)

geo.intersects(location, geography'POLYGON ((30 10, 10 20, 20 40, 40 40, 30 10))')

Spatial Relationship Functions

bool st_equals

st_equals(location, geography'POINT (30 10)')

bool st_disjoint

st_disjoint(location, geography'POLYGON ((30 10, 10 20, 20 40, 40 40, 30 10))')

bool st_touches

st_touches(location, geography'LINESTRING (30 10, 10 30, 40 40)')

bool st_within

st_within(location, geography'POLYGON ((30 10, 10 20, 20 40, 40 40, 30 10))')

bool st_overlaps

st_overlaps(location, geography'POLYGON ((30 10, 10 20, 20 40, 40 40, 30 10))')

bool st_crosses

st_crosses(location, geography'LINESTRING (30 10, 10 30, 40 40)')

bool st_intersects

st_intersects(location, geography'LINESTRING (30 10, 10 30, 40 40)')

bool st_contains

st_contains(location, geography'POINT (30 10)')

bool st_relate

st_relate(location, geography'POLYGON ((30 10, 10 20, 20 40, 40 40, 30 10))', 'T********')

Responses that include only a partial set of the items identified by the request URL SHALL contain a link that allows retrieving the next partial set of items. This link is called a nextLink; its representation is format-specific. The final partial set of items SHALL NOT contain a nextLink.

The nextLink annotation indicates that a response is only a subset of the requested collection of entities or collection of entity references. It contains a URL that allows retrieving the next subset of the requested collection.

SensorThings clients SHALL treat the URL of the nextLink as opaque, and SHALL NOT append system query options to the URL of a next link. Services may not allow a change of format on requests for subsequent pages using the next link.

[Adapted from OData 4.0-Protocol 11.2.5.7]

http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/pagination

Example 25:

http://example.org/v1.1/Things

returns a subset of the Thing entities of requested collection of Things. The nextLink contains a link allowing retrieving the next partial set of items.

Example Response:
{
  "value": [
    {…},
    {…}
  ],
  "@iot.nextLink": "http://examples.org/v1.1/Things?$top=100&$skip=100"
}

10. SensorThings Sensing Create-Update-Delete

Requirements Class

http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete

Target Type

Web Service

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/create-entity

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/link-to-existing-entities

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/deep-insert

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/deep-insert-status-code

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/update-entity

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/update-entity-put

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/update-entity-jsonpatch

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/delete-entity

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/historical-location-auto-creation

Dependency

http://docs.oasis-open.org/odata/odata/v4.0/errata02/os/complete/part1-protocol/odata-v4.0-errata02-os-part1-protocol-complete.html#_Toc406398328

Dependency

http://docs.oasis-open.org/odata/odata/v4.0/errata02/os/complete/part1-protocol/odata-v4.0-errata02-os-part1-protocol-complete.html#_Toc406398329

10.1. Overview

As many IoT devices are resource-constrained, the SensorThings API adopts the efficient REST web service style. That means the Create, Update, Delete actions can be performed on the SensorThings entity types. The following subsection explains the Create, Update, and Delete protocol.

10.2. Create an entity

To create an entity in a collection, the client SHALL send a HTTP POST request to that collection’s URL. The POST body SHALL contain a single valid entity representation.

If the target URL for the collection is a navigationLink, the new entity is automatically linked to the entity containing the navigationLink.

Upon successful completion, the response SHALL contain a HTTP location header that contains the selfLink of the created entity.

Upon successful completion the service SHALL respond with either 201 Created, or 204 No Content.

[Adapted from Data 4.0-Protocol, 11.4.2 Create an Entity]

In addition, the link between entities SHALL be established upon creating an entity. Two use cases SHALL be considered: (1) link to existing entities when creating an entity, and (2) create related entities when creating an entity. The requests for these two use cases are described in the following subsection.

When clients create resources in a SensorThings service, they SHALL follow the integrity constraints listed in Table 24. For example, a Datastream entity SHALL link to a Thing entity. When a client wants to create a Datastream entity, the client needs to either (1) create a linked Thing entity in the same request or (2) link to an already created Thing entity. The complete integrity constraints for creating resources are shown in the following table.

Special case #1 - When creating an Observation entity that links to a FeatureOfInterest entity: Sometimes the FeatureOfInterest of an Observation is the Location of the Thing. For example, a wifi-connected thermostat’s temperature observation’s feature-of-interest can be the location of the smart thermostat, that is the room where the smart thermostat is located in.

In this case, when a client creates an Observation entity, the client SHOULD omit the link to a FeatureOfInterest entity in the POST body message and SHOULD not create a related FeatureOfInterest entity with deep insert. And if the service detects that there is no link to a FeatureOfInterest entity in the POST body message that creates an Observation entity, the service SHALL either (1) create a FeatureOfInterest entity by using the location property from the Location of the Thing entity when there is no FeatureOfInterest whose location property is from the Location of the Thing entity or (2) link to the FeatureOfInterest whose location property is from the Location of the Thing entity.

Special case #2: In the context of IoT, many Observations’ resultTime and phenomenonTime cannot be distinguished or the resultTime is not available. In this case, when a client creates an Observation entity, the client MAY omit the resultTime and the service SHOULD assign a null value to the resultTime.

http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/create-entity
Table 24. Integrity constraints when creating an entity
Scenario Integrity Constraints

Create a Thing entity

-

Create a Location entity

-

Create a Datastream entity

SHALL link to a Thing entity.

SHALL link to a Sensor entity

SHALL link to an ObservedProperty entity.

Create a Sensor entity

-

Create an ObservedProperty entity

-

Create an Observation entity

SHALL link to a Datastream entity.

SHALL link to a FeatureOfInterest entity. If no link specified, the service SHALL create a FeatureOfInterest entity from the content of the Location entities.

Create a FeatureOfInterest entity

-

10.2.1. Request

HTTP Method

POST

URI Pattern

SERVICE_ROOT_URI/COLLECTION_NAME

Header

Content-Type: application/json

Message Body

A single valid entity representation for the specified collection.

Example 26: create a Thing entity

POST /v1.1/Things HTTP/1.1

Host: example.org/
Content-Type: application/json

{
  "name": "thermostat",
  "description":"This is a smart thermostat with WiFi communication capabilities."
}

Example 27: create an Observation entity, which links to an existing Sensor entity (whose id is 1), an existing FeatureOfInterest entity (whose id is 2).

POST /v1.1/Observations HTTP/1.1
Host: example.org
Content-Type: application/json

{
  "Datastream": {
    "@iot.id": 1
  },
  "phenomenonTime": "2013-04-18T16:15:00-07:00",
  "result": 124,
  "FeatureOfInterest": {
    "@iot.id": 2
  }
}

A request to create an entity that includes related entities, represented using the appropriate inline representation, is referred to as a "deep insert". A SensorThings service that supports entity creation SHALL support deep insert.

If the inline representation contains a value for a computed property (i.e., id), the service SHALL ignore that value when creating the related entity.

On success, the service SHALL create all entities and relate them. On failure, the service SHALL NOT create any of the entities.

[Adapted from Data 4.0-Protocol 11.4.2.2]

http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/deep-insert

Example 28: create a Thing while creating two related Sensors and one related Observation (which links to an existing FeatureOfInterest entity and an existing ObservedProperty entity).

POST /v1.1/Things HTTP1.1
Host: example.org
Content-Type: application/json

{
  "description": "This an oven with a temperature datastream.",
  "name": "oven",
  "Locations": [
    {
      "name": "CCIT",
      "description": "Calgary Centre for Innovative Technologies",
      "encodingType": "application/geo+json",
      "location": {
        "type": "Feature",
        "geometry": {
          "type": "Point",
          "coordinates": [10,10]
        }
      }
    }
  ],
  "Datastreams": [
    {
      "name": "oven temperature",
      "description": "This is a datastream for an oven’s internal temperature.",
      "unitOfMeasurement": {
        "name": "degree Celsius",
        "symbol": "°C",
        "definition": "http://unitsofmeasure.org/ucum.html#para-30"
      },
      "observationType": "http://www.opengis.net/def/observationType/OGC-OM/2.0/OM_Measurement",
      "observedArea": {
        "type": "Polygon",
        "coordinates": [[[100,0], [101,0], [101,1], [100,1], [100,0]]]
      },
      "phenomenonTime": "2009-01-11T16:22:25.00Z/2011-08-21T08:32:10.00Z",
      "Observations": [
        {
          "phenomenonTime": "2012-06-26T03:42:02-0600",
          "result": 70.4,
          "FeatureOfInterest": {
            "name": "CCIT #361",
            "description": "This is CCIT #361, Noah’s dad’s office",
            "encodingType": "application/geo+json",
            "feature": {
              "type": "Feature",
              "geometry": {
                "type": "Polygon",
                "coordinates": [
                  [[100,50], [10,9], [23,4], [100,50]], [[30,20], [10,4], [4,22], [30,20]]
                ]
              }
            }
          }
        }
      ],
      "ObservedProperty": {
        "name": "DewPoint Temperature",
        "definition": "http://sweet.jpl.nasa.gov/ontology/property.owl#DewPointTemperature",
        "description": "The dewpoint temperature is the temperature to which the air
                        must be cooled, at constant pressure, for dew to form. As
                        the grass and other objects near the ground cool to the
                        dewpoint, some of the water vapor in the atmosphere
                        condenses into liquid water on the objects."
      },
      "Sensor": {
        "name": "DS18B20",
        "description": "DS18B20 is an air temperature sensor…",
        "encodingType": "application/pdf",
        "metadata": "http://datasheets.maxim-ic.com/en/ds/DS18B20.pdf"
      }
    }
  ]
}

10.2.2. Response

Upon successfully creating an entity, the service response SHALL contain a Location header that contains the URL of the created entity. Upon successful completion the service SHALL respond with 201 Created. Regarding all the HTTP status code, please refer to the HTTP Status Code section.

http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/deep-insert-status-code

10.3. Update an entity

To update an entity in a collection a SensorThings service SHALL follow the requirements as defined in Section 10.3.

http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/update-entity

A SensorThings service that supports updates with PUT SHALL follow the requirements as defined in Section 10.3.

http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/update-entity-put

A SensorThings service that supports updates with the JSON PATCH format SHALL follow the requirements as defined in Section 10.3.

http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/update-entity-jsonpatch

10.3.1. Request

In SensorThings PATCH is the preferred means of updating an entity. PATCH provides more resiliency between clients and services by directly modifying only those values specified by the client.

The semantics of PATCH, as defined in [RFC5789], are to merge the content in the request payload with the entity’s current state, applying the update only to those components specified in the request body. The properties provided in the payload corresponding to updatable properties SHALL replace the value of the corresponding property in the entity. Missing properties of the containing entity or complex property SHALL NOT be directly altered.

Services MAY additionally support PUT, but should be aware of the potential for data-loss in round-tripping properties that the client may not know about in advance, such as open or added properties, or properties not specified in metadata. Services that do not support PUT SHALL respond with an HTTP code 501 Not Implemented.

Services that support PUT SHALL replace all values of structural properties with those specified in the request body. Omitting a non-nullable property with no service-generated or default value from a PUT request results in a 400 Bad Request error.

Key and other non-updatable properties that are not tied to key properties of the principal entity, can be omitted from the request. If the request contains a value for one of these properties, the service SHALL ignore that value when applying the update.

The service ignores the entity id in the payload when applying the update.

The entity SHALL NOT contain related entities as inline content. It MAY contain binding information for navigation properties. For single-valued navigation properties this replaces the relationship. For collection-valued navigation properties this adds to the relationship.

On success, the response SHALL be a valid success response.

Services MAY additionally support JSON PATCH format [RFC6902] to express a sequence of operations to apply to a SensorThings entity.

[Adapted from OData 4.0-Protocol 11.4.3]
HTTP Method

PATCH or PUT

URI Pattern

An URI addressing to a single entity.

Header

Content-Type: application/json

Message Body

A single entity representation including a subset of properties for the specified collection.

Example 29: update the Thing whose id is 1.

PATCH /v1.1/Things(1) HTTP1.1
Host: example.org
Content-Type: application/json

{
  "description":"This thing is an oven."
}

10.3.2. Response

On success, the response SHALL be a valid success response. In addition, when the client sends an update request to a valid URL where an entity does not exist, the service SHALL fail the request.

Upon successful completion, the service must respond with 200 OK or 204 No Content. Regarding all the HTTP status code, please refer to the HTTP Status Code section.

10.4. Delete an entity

To delete an entity in a collection a SensorThings service SHALL follow the requirements as defined in Section 10.4.

http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/delete-entity

10.4.1. Request

A successful DELETE request to an entity’s edit URL deletes the entity. The request body SHOULD be empty.

Services SHALL implicitly remove relations to and from an entity when deleting it; clients need not delete the relations explicitly.

Services MAY implicitly delete or modify related entities if required by integrity constraints. Table 25 lists SensorThings API’s integrity constraints when deleting an entity.

HTTP Method

DELETE

URI Pattern

An URI addressing to a single entity.

Example 30: delete the Thing with unique identifier equals to 1

DELETE http://example.org/v1.1/Things(1)
Table 25. Integrity constraints when deleting an entity
Scenario Integrity Constraints

Delete a Thing entity

Delete all the Datastream and HistoricalLocation entities linked to the Thing entity.

Delete a Location entity

Delete all the HistoricalLocation entities linked to the Location entity

Delete a Datastream entity

Delete all the Observation entities linked to the Datastream entity.

Delete a Sensor entity

Delete all the Datastream entities linked to the Sensor entity.

Delete an ObservedProperty entity

Delete all the Datastream entities linked to the ObservedProperty entity.

Delete an Observation entity

-

Delete a FeatureOfInterest entity

Delete all the Observation entities linked to the FeatureOfInterest entity.

Delete a HistoricalLocation entity entity

-

11. Batch Requests

Requirements Class

http://www.opengis.net/spec/iot_sensing/1.1/req/batch-request

Target Type

Web Service

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/batch-request/batch-request

Dependency

http://docs.oasis-open.org/odata/odata/v4.0/errata02/os/complete/part1-protocol/odata-v4.0-errata02-os-part1-protocol-complete.html#_Toc406398359

The batch-processing of the SensorThings service SHALL be as defined in Chapter 11.

http://www.opengis.net/spec/iot_sensing/1.1/req/batch-request/batch-request

11.1. Introduction

The SensorThings service interface provides interfaces for users to perform CRUD actions on resources through different HTTP methods. However, as many IoT devices are resource-constrained, handling a large number of communications may not be practical. This section describes how a SensorThings service can support executing multiple operations sent in a single HTTP request through the use of batch processing. This section covers both how batch operations are represented and processed. SensorThings batch request extension is adapted from [OData 4.0 Protocol 11.7] and all subsections. The only difference is that the OData-Version header SHOULD be omitted in SensorThings. Readers are encouraged to read the OData specification section 11.7 before reading the examples below.

11.2. Batch-processing request

A batch request is represented as a Multipart MIME v1.0 message [RFC2046], a standard format allowing the representation of multiple parts, each of which may have a different content type, within a single request.

The example below shows a GUID as a boundary and example.org/v1.1/ for the URI of the service.

Batch requests are submitted as a single HTTP POST request to the batch endpoint of a service, located at the URL $batch relative to the service root (e.g., example.org/v1.1/$batch).

Note: In the example, request bodies are excluded in favor of English descriptions inside <> brackets to simplify the example.

Example 31-1: A Batch Request header example

POST /v1.1/$batch HTTP/1.1
Host: example.org
Content-Type: multipart/mixed;boundary=batch_36522ad7-fc75-4b56-8c71-56071383e77b

<BATCH_REQUEST_BODY>

Note: The batch request boundary must be quoted if it contains any of the following special characters:

  ( ) < > @
  , ; :  / " [ ] ? =

11.2.1. Batch request body example

The following example shows a Batch Request that contains the following operations in the order listed:

  • A query request

  • Change Set that contains the following requests:

  • Insert entity (with Content-ID = 1)

  • Update request (with Content-ID = 2)

  • A second query request

Note: For brevity, in the example, request bodies are excluded in favor of English descriptions inside <> brackets.

Note also that the two empty lines after the Host header of the GET request are necessary: the first is part of the GET request header; the second is the empty body of the GET request, followed by a CRLF according to [RFC2046].

Example 31-2: a Batch Request body example

POST /v1.1/$batch HTTP/1.1
Host: host
Content-Type: multipart/mixed;boundary=batch_36522ad7-fc75-4b56-8c71-56071383e77b
Content-Length: ###

--batch_36522ad7-fc75-4b56-8c71-56071383e77b
Content-Type: application/http

GET /v1.1/Things(1)
Host: host


--batch_36522ad7-fc75-4b56-8c71-56071383e77b
Content-Type: multipart/mixed;boundary=changeset_77162fcd-b8da-41ac-a9f8-9357efbbd

--changeset_77162fcd-b8da-41ac-a9f8-9357efbbd

Content-Type: application/http

Content-ID: 1

POST /v1.1/Things HTTP/1.1
Host: host
Content-Type: application/json

Content-Length: ###

<JSON representation of a new Thing>
--changeset_77162fcd-b8da-41ac-a9f8-9357efbbd

Content-Type: application/http

Content-ID: 2

PATCH /v1.1/Things(1) HTTP/1.1

Host: host
Content-Type: application/json

Content-Length: ###

<JSON representation of Things(1)>
--changeset_77162fcd-b8da-41ac-a9f8-9357efbbd--
--batch_36522ad7-fc75-4b56-8c71-56071383e77b

Content-Type: application/http

GET /v1.1/Things(3) HTTP/1.1
Host: host


--batch_36522ad7-fc75-4b56-8c71-56071383e77b--

11.2.2. Referencing new entities in a change set example

Create and update actions inside a change set can reference entities previously created inside the same change set. To make a created entity referenceable, the POST that creates the entity must have a Content-ID header, the content of which can be any string. Subsequent requests in the same change set can now use the value of this header, prefixed with a $, in places where the ID of the created entity is required. To ensure valid JSON, the resulting value will have to be encoded as a string.

Example 31-3: A Batch Request that contains the following operations in the order listed:

A batch request, containing a single change set that contains the following requests:

  1. Insert a new Sensor entity (with Content-ID = sensor1)

  2. Insert a new Datastream entity, referencing the previously created Sensor entity as "$sensor1".

POST /v1.1/$batch HTTP/1.1
Host: host
Content-Type: multipart/mixed;boundary=batch_36522ad7-fc75-4b56-8c71-56071383e77b

--batch_36522ad7-fc75-4b56-8c71-56071383e77b
Content-Type: multipart/mixed;boundary=changeset_77162fcd-b8da-41ac-a9f8-9357efbbd

--changeset_77162fcd-b8da-41ac-a9f8-9357efbbd
Content-Type: application/http
Content-ID: sensor1

POST /v1.1/Sensors HTTP/1.1
Host: host
Content-Type: application/json
Content-Length: ###

{
  "name": "DS18B20",
  "description": "DS18B20 is an air temperature sensor",
  "encodingType": "application/pdf",
  "metadata": "http://datasheets.maxim-ic.com/en/ds/DS18B20.pdf"
}
--changeset_77162fcd-b8da-41ac-a9f8-9357efbbd
Content-Type: application/http

POST /v1.1/Things(5)/Datastreams HTTP/1.1
Host: host
Content-Type: application/json
Content-Length: ###

{
  "name": "Temperature Thing 5",
  "description": "The temperature of thing 5",
  "ObservedProperty: {"@iot.id": 12},
  "Sensor": {"@iot.id": "$sensor1"}
}
--changeset_77162fcd-b8da-41ac-a9f8-9357efbbd--
--batch_36522ad7-fc75-4b56-8c71-56071383e77b--

11.3. Batch-processing response

Example 31-4: referencing the batch request Example 31-2 above, assume all the requests except the final query request succeed. In this case the response would be:

HTTP/1.1
200 Ok
Content-Length: ####
Content-Type: multipart/mixed;boundary=b_243234_25424_ef_892u748

--b_243234_25424_ef_892u748
Content-Type: application/http

HTTP/1.1 200 Ok
Content-Type: application/json
Content-Length: ###

<JSON representation of the Thing entity with id = 1>
--b_243234_25424_ef_892u748
Content-Type: multipart/mixed;boundary=cs_12u7hdkin252452345eknd_383673037

--cs_12u7hdkin252452345eknd_383673037
Content-Type: application/http
Content-ID: 1

HTTP/1.1 201 Created
Content-Type: application/json
Location: http://host/v1.1/Things(99)
Content-Length: ###

<JSON representation of a new Thing entity>

--cs_12u7hdkin252452345eknd_383673037
Content-Type: application/http
Content-ID: 2

HTTP/1.1 204 No Content
Host: host


--cs_12u7hdkin252452345eknd_383673037--
--b_243234_25424_ef_892u748
Content-Type: application/http

HTTP/1.1 404 Not Found
Content-Type: application/json
Content-Length: ###

<Error message>
--b_243234_25424_ef_892u748--

11.4. Asynchronous batch requests

Example 31-5: referencing the Example 31-2 above again, assume that when interrogating the monitor URL for the first time only the first request in the batch finished processing and all the remaining requests except the final query request succeed. In this case the response would be:

HTTP/1.1 200 Ok
Content-Length: ####
Content-Type: multipart/mixed;boundary=b_243234_25424_ef_892u748

--b_243234_25424_ef_892u748
Content-Type: application/http

HTTP/1.1 200 Ok
Content-Type: application/json
Content-Length: ###

<JSON representation of the Thing entity with id = 1>
--b_243234_25424_ef_892u748
Content-Type: application/http

HTTP/1.1 202 Accepted
Location: http://service-root/async-monitor
Retry-After: ###


--b_243234_25424_ef_892u748--

Client makes a second request using the returned monitor URL:

HTTP/1.1 200 Ok
Content-Length: ####
Content-Type: multipart/mixed;boundary=b_243234_25424_ef_892u748

--b_243234_25424_ef_892u748
Content-Type: multipart/mixed;boundary=cs_12u7hdkin252452345eknd_383673037

--cs_12u7hdkin252452345eknd_383673037
Content-Type: application/http
Content-ID: 1

HTTP/1.1 201 Created
Content-Type: application/json
Location: http://host/v1.1/Things(99)
Content-Length: ###

<JSON representation of a new Thing entity>
--cs_12u7hdkin252452345eknd_383673037
Content-Type: application/http
Content-ID: 2

HTTP/1.1 204 No Content
Host: host


--cs_12u7hdkin252452345eknd_383673037--
--b_243234_25424_ef_892u748
Content-Type: application/http

HTTP/1.1 404 Not Found
Content-Type: application/json
Content-Length: ###

<Error message>
--b_243234_25424_ef_892u748—

12. SensorThings MultiDatastream extension

Requirements Class

http://www.opengis.net/spec/iot_sensing/1.1/req/multi-datastream

Target Type

Web Service

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/multi-datastream/properties

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/multi-datastream/relations

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/multi-datastream/constraints

Observation results may have many data types, including primitive types like category or measure, but also more complex types such as time, location and geometry [OGC 10-004r3 and ISO 19156:2011]. SensorThings’ MultiDatastream entity is an extension to handle complex observations when the result is an array.

A MultiDatastream groups a collection of Observations and the Observations in a MultiDatastream have a complex result type.

The MultiDatastream extension entities are depicted in Figure 3.

MultiDatastream Extension Entities
Figure 3. MultiDatastream Extension Entities

Each MultiDatastream entity SHALL have the mandatory properties and MAY have the optional properties listed in Table 26.

http://www.opengis.net/spec/iot_sensing/1.1/req/multi-datastream/properties

Each MultiDatastream entity SHALL have the direct relation between a MultiDatastream entity and other entity types listed in Table 27.

http://www.opengis.net/spec/iot_sensing/1.1/req/multi-datastream/relations
Table 26. Properties of a MultiDatastream entity
Name Definition Data type Multiplicity and use

name

A property provides a label for Datastream entity, commonly a descriptive name.

CharacterString

One (mandatory)

description

The description of the Datastream entity.

CharacterString

One (mandatory)

unitOfMeasurements

A JSON array of JSON objects that containing three key-value pairs. The name property presents the full name of the unitOfMeasurement; the symbol property shows the textual form of the unit symbol; and the definition contains the URI defining the unitOfMeasurement. (see Req 42 for the constraints between unitOfMeasurement, multiObservationDataType and result).

A JSON array

One (mandatory)

Note: It is possible an observation does not have a unit of measurement. For example, a count observation does not have a unit of measurement.

observationType

The type of Observation (with unique result type), which is used by the service to encode observations.

ValueCode and its value SHALL be OM_ComplexObservation.

One (mandatory)

multiObservationDataTypes

This property defines the observationType of each element of the result of a complex Observation.

A JSON array of ValueCode. See Table 12 for the available ValueCodes.

One
(mandatory)

properties

A JSON Object containing user-annotated properties as key-value pairs.

JSON Object

Zero-to-one

observedArea

The spatial bounding box of the spatial extent of all FeatureOfInterests that belong to the Observations associated with this MultiDatastream.

GM_Envelope (GeoJSON Polygon)

Zero-to-one

phenomenonTime

The temporal interval of the phenomenon times of all observations belonging to this MultiDatastream.

TM_Period (ISO 8601 Time Interval)

Zero-to-one

resultTime

The temporal interval of the result times of all observations belonging to this MultiDatastream.

TM_Period (ISO 8601 Time Interval)

Zero-to-one
Table 27. Direct relation between a MultiDatastream entity and other entity types
Entity type Relation Description

Thing

Many optional to one mandatory

A Thing has zero-to-many MultiDatastream. A MultiDatastream entity SHALL only link to a Thing as a collection of Observations.

Sensor

Many optional to one mandatory

The Observations in a MultiDatastream are performed by one-and-only-one Sensor. One Sensor MAY produce zero-to-many Observations in different MultiDatastreams.

ObservedProperty

Many optional to many mandatory

The Observations of a MultiDatastream SHALL observe the same ObservedProperties entity set.

Observation

One mandatory to many optional

A MultiDatastream has zero-to-many Observations. One Observation SHALL occur in one-and-only-one MultiDatastream.
Table 28. Direct relation between an MultiDatastream’s Observation entity and other entity types
Entity type Relation Description

MultiDatastream

Many optional to one mandatory

A MultiDatastream can have zero-to-many Observations. One Observation SHALL occur in one-and-only-one MultiDatastream.

FeatureOfInterest

Many optional to one mandatory

An Observation observes on one-and-only-one FeatureOfInterst. One FeatureOfInterest could be observed by one-to-many Observations.

The size and the order of each element of a MultiDatastream’s unitOfMeasurements array (i.e., MultiDatastream(id)/unitOfMeasurements) SHALL match the size and the order of each element of the related ObservedProperties collection (i.e., MultiDatastreams(id)/ObservedProperties).

The size and the order of each element of a MultiDatastream’s unitOfMeasurements array (i.e., MultiDatastreams(id)/unitOfMeasurements) SHALL match the size and the order of each element of all related Observations’ result (i.e., MultiDatastreams(id)/Observations?$select=result).

The size and the order of each element of a MultiDatastream’s unitOfMeasurements array (i.e., MultiDatastreams(id)/unitOfMeasurements) SHALL match the size and the order of each element of the MultiDatastream’s multiObservationDataTypes array (i.e., MultiDatastreams(id)/multiObservationDataTypes).

When a complex result’s element does not have a unit of measurement (e.g., a OM_TruthObservation type), the corresponding unitOfMeasurement element SHALL have null values.

http://www.opengis.net/spec/iot_sensing/1.1/req/multi-datastream/constraints

Example 32: MultiDatastream entity example 1

 {
  "@iot.id": 1,
  "@iot.selfLink": "http://example.org/v1.1/MultiDatastreams(1)",
  "Thing@iot.navigationLink": "MultiDatastreams(1)/Thing",
  "Sensor@iot.navigationLink": "MultiDatastreams(1)/Sensor",
  "ObservedProperty@iot.navigationLink": "MultiDatastreams(1)/ObservedProperties",
  "Observations@iot.navigationLink": "MultiDatastreams/Observations",
  "name": "temperature, RH, visibility",
  "description": "This is a MultiDatastream from a simple weather station measuring air temperature, relative humidity and visibility",
  "observationType": "http://www.opengis.net/def/observationType/OGC-OM/2.0/OM_ComplexObservation",
  "multiObservationDataTypes": [
    "http://www.opengis.net/def/observationType/OGC-OM/2.0/OM_Measurement",
    "http://www.opengis.net/def/observationType/OGC-OM/2.0/OM_Measurement",
    "http://www.opengis.net/def/observationType/OGC-OM/2.0/OM_CategoryObservation"
  ],
  "unitOfMeasurements": [
    {
      "name": "degree Celsius",
      "symbol": "°C",
      "definition": "http://unitsofmeasure.org/ucum.html#para-30"
    },
    {
      "name": "percent",
      "symbol": "%",
      "definition": "http://unitsofmeasure.org/ucum.html#para-29"
    },
    {
      "name": "null",
      "symbol": "null",
      "definition": "null"
    }
  ],
  "observedArea": {
    "type": "Polygon",
    "coordinates": [
      [
        [100, 0], [101, 0], [101, 1], [100, 1], [100, 0]
      ]
    ]
  },
  "phenomenonTime": "2014-03-01T13:00:00Z/2015-05-11T15:30:00Z",
  "resultTime": "2014-03-01T13:00:00Z/2015-05-11T15:30:00Z"
}

Example 33: an example ObservedProperties collection of the above MultiDatastream: Please note that the order of the elements in the value array match the order of the related Observations/result array as well as the order of the related unitOfMeasurements array.

{
  "value": [
    {
      "@iot.id": 1,
      "@iot.selfLink": "http://example.org/v1.1/ObservedProperties(1)",
      "Datastreams@iot.navigationLink": "ObservedProperties(1)/Datastreams",
      "MultiDatastreams@iot.navigationLink": "ObservedProperties(1)/ MultiDatastreams",
      "description": "The dew point is the temperature at which the water vapor in a sample
                      of air at constant barometric pressure condenses into liquid water at the
                      same rate at which it evaporates. At temperatures below the dew point, water
                      will leave the air.",
      "name": "Dew point temperature"
    },
    {
      "@iot.id ": 2,
      "@iot.selfLink": "http://example.org/v1.1/ObservedProperties(2)",
      "Datastreams@iot.navigationLink": "ObservedProperties(2)/Datastreams",
      "MultiDatastreams@iot.navigationLink": "ObservedProperties(2)/ MultiDatastreams",
      "description": "Relative humidity (abbreviated RH) is the ratio of the partial pressure
                      of water vapor to the equilibrium vapor pressure of water at the same
                      temperature.",
      "name": "Relative Humidity"
    },
    {
      "@iot.id": 3,
      "@iot.selfLink": "http://example.org/v1.1/ObservedProperties(3)",
      "Datastreams@iot.navigationLink": "ObservedProperties(3)/Datastreams",
      "MultiDatastreams@iot.navigationLink": "ObservedProperties(3)/MultiDatastreams",
      "description": "Visibility is a measure of the distance at which an object or light can
                      be clearly discerned. ",
      "name": "Visibility (Weather)"
    }
  ]
}

Example 34: an example Observation of the above MultiDatastream: Please note that the order of the elements in the result array match (1) the order of the related ObservedProperties (i.e., Observation(id)/MultiDatastreams(id)/ObservedProperties ), (2) the order of the related unitOfMeasurements array (i.e., Observation(id)/ MultiDatastream(id)/unitOfMeasurements ) and (3) the order of the related multiObservationDataTypes (i.e., Observation(id)/MultiDatastream(id)/multiObservationDataTypes).

{
  "@iot.id": 1,
  "@iot.selfLink": "http://example.org/v1.1/Observations(1)",
  "FeatureOfInterest@iot.navigationLink": "Observations(1)/FeatureOfInterest",
  "MultiDatastream@iot.navigationLink": "Observations(1)/MultiDatastream",
  "phenomenonTime": "2014-12-31T11:59:59.00+08:00",
  "resultTime": "2014-12-31T11:59:59.00+08:00",
  "result": [
    25,
    65,
    "clear"
  ]
}

13. SensorThings Data Array Extension

Requirements Class

http://www.opengis.net/spec/iot_sensing/1.1/req/data-array

Target Type

Web Service

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/data-array/data-array

To support the SensorThings data array extension, a service SHALL support the retrieval and creation of observations as defined in Chapter 13.

http://www.opengis.net/spec/iot_sensing/1.1/req/data-array/data-array

Similar to the SWE DataArray in the OGC SOS, SensorThings API also provides the support of dataArray (in addition to formatting every observation entity as a JSON object) to aggregate multiple Observation entities and reduce the request (e.g., POST) and response (e.g., GET) size. SensorThings mainly use dataArray in two scenarios: (1) get Observation entities in dataArray, and (2) create Observation entities with dataArray.

13.1. Retrieve a Datastream’s Observation entities in dataArray

In SensorThings services, users are able to request for multiple Observation entities and format the entities in the dataArray format. When a SensorThings service returns a dataArray response, the service groups Observation entities by Datastream or MultiDatastream, which means the Observation entities that link to the same Datastream or the same MultiDatastream are aggregated in one dataArray.

13.1.1. Request

In order to request for dataArray, users must include the query option $resultFormat=dataArray when requesting Observation entities. For example, http://example.org/v1.1/Observations?$resultFormat=dataArray. The query options $select, $top, $skip, $count and $orderby work the same as they would with a non-dataArray request, only the formatting of the result is different, as the Observations are grouped by (Multi)Datastream. The result can contain @iot.count and @iot.nextLink fields just like with normal requests for Observations. The $expand query parameter is not allowed for dataArray requests.

13.1.2. Response

The response Observations in dataArray format contains the following properties.

Table 29. Properties of getting Observation entities in dataArray
Name Definition Data type Multiplicity and use

Datastream or MultiDatastream

The navigationLink of the Datastream or the MultiDatastream entity used to group Observation entities in the dataArray.

navigationLink

One (mandatory)

components

An ordered array of Observation property names whose matched values are included in the dataArray.

An ordered array of Observation property names

One (mandatory)

dataArray

A JSON Array containing Observation entities. Each Observation entity is represented by the ordered property values, which match with the ordered property names in components.

JSON Array

One (mandatory)

Example 35: an example of getting Observation entities from a Datastream in dataArray result format:

GET /v1.1/Datastreams(1)/Observations?$resultFormat=dataArray
HTTP/1.1 200 OK
Host: www.example.org
Content-Type: application/json

{
  "@iot.nextLink": "http://example.org/v1.1/Datastreams(1)/Observations?$resultFormat=dataArray&$skip=3",
  "@iot.count": 42,
  "value": [
    {
      "Datastream@iot.navigationLink": "http://example.org/v1.1/Datastreams(1)",
      "components": [
        "id",
        "phenomenonTime",
        "resultTime",
        "result"
      ],
      "dataArray": [
        [
          1,
          "2005-08-05T12:21:13Z",
          "2005-08-05T12:21:13Z",
          20
        ],
        [
          2,
          "2005-08-05T12:22:08Z",
          "2005-08-05T12:21:13Z",
          30
        ],
        [
          3,
          "2005-08-05T12:22:54Z",
          "2005-08-05T12:21:13Z",
          0
        ]
      ]
    }
  ]
}

Example 36: an example of getting Observation entities from a MultiDatastream in dataArray result format

GET /v1.1/MultiDatastreams(1)/Observations?$resultFormat=dataArray
HTTP/1.1 200 OK
Host: www.example.org
Content-Type: **application/json

{
  "@iot.nextLink": "http://example.org/v1.1/MultiDatastreams(1)/Observations?$resultFormat=dataArray&$skip=3",
  "@iot.count": 42,
  "value": [
    {
      "MultiDatastream@iot.navigationLink": "http://example.org/v1.1/MultiDatastreams(1)",
      "components": [
        "id",
        "phenomenonTime",
        "resultTime",
        "result"
      ],
      "dataArray": [
        [
          1,
          "2010-12-23T11:20:00-0700",
          "2010-12-23T11:20:00-0700",
          [
            10.2,
            65,
            "clear"
          ]
        ],
        [
          2,
          "2010-12-23T11:22:08-0700",
          "2010-12-23T11:20:00-0700",
          [
            11.3,
            63,
            "clear"
          ]
        ],
        [
          3,
          "2010-12-23T11:22:54-0700",
          "2010-12-23T11:20:00-0700",
          [
            9.8,
            67,
            "clear"
          ]
        ]
      ]
    }
  ]
}

13.2. Create Observation entities with dataArray

Besides creating Observation entities one by one with multiple HTTP POST requests, there is a need to create multiple Observation entities with a lighter message body in a single HTTP request. In this case, a sensing system can buffer multiple Observations and send them to a SensorThings service in one HTTP request. Here we propose an Action operation CreateObservations.

13.2.1. Request

Users can invoke the CreateObservations action by sending a HTTP POST request to the SERVICE_ROOT_URL/CreateObservations.

For example, http://example.org/v1.1/CreateObservations.

The message body aggregates Observations by Datastreams, which means all the Observations linked to one Datastream SHALL be aggregated in one JSON object. The parameters of each JSON object are shown in the following table.

As an Observation links to one FeatureOfInterest, to establish the link between an Observation and a FeatureOfInterest, users should include the FeatureOfInterest ids in the dataArray. If no FeatureOfInterest id presented, the FeatureOfInterest will be created based on the Location entities of the linked Thing entity by default.

Table 30. Properties of creating Observation entities with dataArray
Name Definition Data type Multiplicity and use

Datastream

The unique identifier of the Datasteam linking to the group of Observation entities in the dataArray.

The unique identifier of a Datastream

One (mandatory)

components

An ordered array of Observation property names whose matched values are included in the dataArray. At least the phenomenonTime and result properties SHALL be included. To establish the link between an Observation and a FeatureOfInterest, the component name is "FeatureOfInterest/id" and the FeatureOfInterest ids should be included in the dataArray array. If no FeatureOfInterest id is presented, the FeatureOfInterest will be created based on the Location entities of the linked Thing entity by default.

An ordered array of Observation property names

One (mandatory)

dataArray

A JSON Array containing Observations. Each Observation is represented by the ordered property values. The ordered property values match with the ordered property names in components.

JSON Array

One (mandatory)

Example 37: example of a request for creating Observation entities in dataArray

POST /v1.1/CreateObservations HTTP/1.1
Host: example.org/
Content-Type: application/json

[
  {
    "Datastream": {
      "@iot.id": 1
    },
    "components": [
      "phenomenonTime",
      "result",
      "FeatureOfInterest/id"
    ],
    "dataArray": [
      [
        "2010-12-23T10:20:00-0700",
        20,
        1
      ],
      [
        "2010-12-23T10:21:00-0700",
        30,
        1
      ]
    ]
  },
  {
    "Datastream": {
      "@iot.id": 2
    },
    "components": [
      "phenomenonTime",
      "result",
      "FeatureOfInterest/id"
    ],
    "dataArray": [
      [
        "2010-12-23T10:20:00-0700",
        65,
        1
      ],
      [
        "2010-12-23T10:21:00-0700",
        60,
        1
      ]
    ]
  }
]

13.2.2. Response

Upon successful completion the service SHALL respond with 201 Created. The response message body SHALL contain the URLs of the created Observation entities, where the order of URLs must match with the order of Observations in the dataArray from the request. In the case of the service having exceptions when creating individual observation entities, instead of responding with URLs, the service must specify "error" in the corresponding array element.

Example 38: an example of a response of creating Observation entities with dataArray

POST /v1.1/CreateObservations HTTP/1.1
201 Created
Host: example.org
Content-Type: application/json

[
  "http://examples.org/v1.1/Observations(1)",
  "error",
  "http://examples.org/v1.1/Observations(2)"
]

14. SensorThings Sensing MQTT Extension

In addition to support HTTP protocol, a SensorThings service MAY support MQTT protocol to enhance the SensorThings service publish and subscribe capabilities. This section describes the SensorThings MQTT extension. To help a client find the MQTT endpoints of a SensorThings service, the endpoints of the service are documented in the serverSettings object of the landing page described in Section 9.2.1. If the service supports the MQTT extension, then the serverSettings object SHALL contain properties of type Object, with the names

http://www.opengis.net/spec/iot_sensing/1.1/req/receive-updates-via-mqtt/receive-updates
http://www.opengis.net/spec/iot_sensing/1.1/req/create-observations-via-mqtt/observations-creation

These Objects SHALL contain a property named endpoints of type Array. The JSON Array endpoints SHALL hold a list of URL Schemes that can be used to connect to the MQTT service, as seen in example 10 in Section 9.2.1. If the service supports both update-notification and observation-creation over MQTT, it may use different endpoints for the two services.

14.1. Create a SensorThings Observation with MQTT Publish

Requirements Class

http://www.opengis.net/spec/iot_sensing/1.1/req/create-observations-via-mqtt

Target Type

Web Service

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/create-observations-via-mqtt/observations-creation

Dependency

http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/mqtt-v3.1.1.html

To allow clients to create observations with MQTT Publish, a service SHALL support the creation of observations with MQTT as defined in Section 14.1.

http://www.opengis.net/spec/iot_sensing/1.1/req/create-observations-via-mqtt/observations-creation

SensorThings MQTT extension provides the capability of creating Observation entity using MQTT protocol. To create an Observation entity in MQTT, the client sends a MQTT Publish request to the SensorThings service and the MQTT topic is the Observations resource path prefixed with the service version number (for example, v1.1/Observations). The MQTT application message contains a single valid Observation entity representation. Figure 4 contains the sequence diagram for creating Observation using MQTT publish as well as MQTT sending notifications for Observation creation.

Creating Observations using MQTT publish
Figure 4. Creating Observations using MQTT publish, and receive notifications for Observations with MQTT

If the MQTT topic for the Observation is a navigationLink from Datastream or FeatureOfInterest, the new Observation entity is automatically linked to that Datastream or FeatureOfInterest respectively.

Similar to creating Observations with HTTP POST, creating Observations with MQTT Publish follow the integrity constraints for creating Observation listed in Table 24. The two special cases defined in Req 33 are also applied in the case of creating Observations with MQTT Publish.

To link to existing entities when creating an Observation entity with MQTT, the conditions in Req 34 is applied.

14.1.2. Create related entities when creating an Observation entity (deep insert)

To create related entities when creating an entity with MQTT, the condition in Req 35 is applied.

14.2. Receive updates with MQTT Subscribe

Requirements Class

http://www.opengis.net/spec/iot_sensing/1.1/req/receive-updates-via-mqtt

Target Type

Web Service

Requirement

http://www.opengis.net/spec/iot_sensing/1.1/req/receive-updates-via-mqtt/receive-updates

Dependency

http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/mqtt-v3.1.1.html

To allow clients to receive notifications for the updates of SensorThings entities with MQTT, a service SHALL support the receiving updates with MQTT Subscribe as defined in Section 14.2.

http://www.opengis.net/spec/iot_sensing/1.1/req/receive-updates-via-mqtt/receive-updates

To receive notifications from a SensorThings service when some entities updated, a client can send a MQTT Subscribe request to the SensorThings service. SensorThings API defined the following four MQTT subscription use cases. Figure 5 contains the sequence diagram of receiving updates using MQTT Subscribe.

Sequence diagram for receiving updates using MQTT subscribe
Figure 5. Sequence diagram for receiving updates using MQTT subscribe

14.2.1. Receive updates of a SensorThings entity set with MQTT Subscribe

MQTT Control Packet: Subscribe

Topic Pattern: SERVICE_VERSION/RESOURCE_PATH/COLLECTION_NAME

Example Topic: v1.1/Datastreams(1)/Observations

Response: When a new entity is added to the entity set (e.g., a new Observation created) or an existing entity of the entity set is updated, the service returns a complete JSON representation of the newly created or updated entity.

14.2.2. Receive updates of a SensorThings entity with MQTT Subscribe

MQTT Control Packet: Subscribe

Topic Pattern: SERVICE_VERSION/RESOURCE_PATH_TO_AN_ENTITY

Example Topic: v1.1/Datastreams(1)

Response:When a property of the subscribed entity is updated, the service returns a complete JSON representation of the updated entity.

14.2.3. Receive updates of a SensorThings entity’s property with MQTT Subscribe

MQTT Control Packet: Subscribe

Topic Pattern: SERVICE_VERSION/RESOURCE_PATH_TO_AN_ENTITY/PROPERTY_NAME

Example Topic: v1.1/Datastreams(1)/observedArea

Response: When the value of the subscribed property is changed, the service returns a JSON object. The returned JSON object follows as defined in Section 9.2.4.

Example 39: an example response of receiving updates of an entity’s property with MQTT Subscribe. The example shows a sample response of the following MQTT topic subscription: v1.1/Datastreams(1)/description

{
  "description": "This is an updated description of a thing"
}

14.2.4. Receive updates of the selected properties of the newly created entities or updated entities of a SensorThings entity set with MQTT Subscribe

MQTT Control Packet: Subscribe

Topic Pattern: SERVICE_VERSION/RESOURCE_PATH/COLLECTION_NAME?$select=PROPERTY_1,PROPERTY_2,…

Response: When a new entity is added to an entity set or an existing entity is updated (e.g., a new Observation created or an existing Observation is updated), the service returns a JSON representation of the selected properties of the newly created or updated entity.

Note: In the case of an entity’s property is updated, it is possible that the selected properties are not the updated property, so that the returned JSON does not reflect the update.

Example 40: an example response of receiving updates of the selected property of an entity set with MQTT Subscribe. The example shows a sample response of the following MQTT topic subscription: v1.1/Datastreams(1)/Observations?$select=phenomenonTime,result

{
  "result": 45,
  "phenonmenonTime": "2015-02-05T17:00:00Z"
}

Annex A: Conformance Class Abstract Test Suite (Normative)

A.1. SensorThings Read (Core) Tests

This section contains the conformance classes for the SensorThings API Read (Core). The SensorThings API service needs to pass all the conformance tests defined in this section.

A.1.1 Conformance class: SensorThings API Entity Control Information

Conformance class id:

http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/entity-control-information

Test: Common Control Information

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/entity-control-information/common-control-information

Requirements

1. http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/entity-control-information/common-control-information

Test purpose

Check if each entity has the common control information as defined in the requirement http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/entity-control-information/common-control-information.

Test method

Inspect the full JSON object of the entity sets (i.e., without $select) to identify, if each entity has the common control information defined in the above requirement and the service sends appropriate responses as defined in this specification.
A.1.2 Conformance class: SensorThings API Thing Entity

Conformance class id:

http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/thing

Test: Thing Entity

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/thing/thing-valid

Requirements

2. http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/thing/properties
3. http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/thing/relations

Test purpose

Check if each Thing entity has the mandatory properties and mandatory relations as defined in this specification.

Test method

Inspect the full JSON object of the Thing entity sets (i.e., without $select) to identify, if each entity has the mandatory properties defined in the corresponding requirement.

Inspect the full JSON object of each Thing entity set (i.e., without using the $select query option) to identify, if each entity has the mandatory relations (i.e., @iot.navigationLink) defined in the corresponding requirement.
A.1.3 Conformance class: SensorThings API Location Entity

Conformance class id:

http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/location

Test: Location Entity

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/location/location-valid

Requirements

4. http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/location/properties
5. http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/location/relations

Test purpose

Check if each Location entity has the mandatory properties and mandatory relations as defined in this specification.

Test method

Inspect the full JSON object of the Location entity sets (i.e., without $select) to identify, if each entity has the mandatory properties defined in the corresponding requirement.

Inspect the full JSON object of each Location entity set (i.e., without using the $select query option) to identify, if each entity has the mandatory relations (i.e., @iot.navigationLink) defined in the corresponding requirement.
A.1.4 Conformance class: SensorThings API HistoricalLocation Entity

Conformance class id:

http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/historical-location

Test: Historicalocation Entity

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/historical-location/historical-location-valid

Requirements

6. http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/historical-location/properties
7. http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/historical-location/relations

Test purpose

Check if each Historicalocation entity has the mandatory properties and mandatory relations as defined in this specification.

Test method

Inspect the full JSON object of the Historicalocation entity sets (i.e., without $select) to identify, if each entity has the mandatory properties defined in the corresponding requirement.

Inspect the full JSON object of each Historicalocation entity set (i.e., without using the $select query option) to identify, if each entity has the mandatory relations (i.e., @iot.navigationLink) defined in the corresponding requirement.
A.1.5 Conformance class: SensorThings API Datastream Entity

Conformance class id:

http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/datastream

Test: Datastream Entity

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/datastream/datastream-valid

Requirements

9. http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/datastream/properties
10. http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/datastream/relations

Test purpose

Check if each Datastream entity has the mandatory properties and mandatory relations as defined in this specification.

Test method

Inspect the full JSON object of the Datastream entity sets (i.e., without $select) to identify, if each entity has the mandatory properties defined in the corresponding requirement.

Inspect the full JSON object of each Datastream entity set (i.e., without using the $select query option) to identify, if each entity has the mandatory relations (i.e., @iot.navigationLink) defined in the corresponding requirement.
A.1.6 Conformance class: SensorThings API Sensor Entity

Conformance class id:

http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/sensor

Test: Sensor Entity

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/sensor/sensor-valid

Requirements

11. http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/sensor/properties
12. http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/sensor/relations

Test purpose

Check if each Sensor entity has the mandatory properties and mandatory relations as defined in this specification.

Test method

Inspect the full JSON object of the Sensor entity sets (i.e., without $select) to identify, if each entity has the mandatory properties defined in the corresponding requirement.

Inspect the full JSON object of each Sensor entity set (i.e., without using the $select query option) to identify, if each entity has the mandatory relations (i.e., @iot.navigationLink) defined in the corresponding requirement.
A.1.7 Conformance class: SensorThings API ObservedProperty Entity

Conformance class id:

http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/observed-property

Test: ObservedProperty Entity

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/observed-property/observed-property-valid

Requirements

13. http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/observed-property/properties
14. http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/observed-property/relations

Test purpose

Check if each ObservedProperty entity has the mandatory properties and mandatory relations as defined in this specification.

Test method

Inspect the full JSON object of the ObservedProperty entity sets (i.e., without $select) to identify, if each entity has the mandatory properties defined in the corresponding requirement.

Inspect the full JSON object of each ObservedProperty entity set (i.e., without using the $select query option) to identify, if each entity has the mandatory relations (i.e., @iot.navigationLink) defined in the corresponding requirement.
A.1.8 Conformance class: SensorThings API Observation Entity

Conformance class id:

http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/observation

Test: Observation Entity

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/observation/observation-valid

Requirements

15. http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/observation/properties
16. http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/observation/relations

Test purpose

Check if each Observation entity has the mandatory properties and mandatory relations as defined in this specification.

Test method

Inspect the full JSON object of the Observation entity sets (i.e., without $select) to identify, if each entity has the mandatory properties defined in the corresponding requirement.

Inspect the full JSON object of each Observation entity set (i.e., without using the $select query option) to identify, if each entity has the mandatory relations (i.e., @iot.navigationLink) defined in the corresponding requirement.
A.1.9 Conformance class: SensorThings API FeatureOfInterest Entity

Conformance class id:

http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/feature-of-interest

Test: FeatureOfInterest Entity

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/feature-of-interest/feature-of-interest-valid

Requirements

17. http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/feature-of-interest/properties
18. http://www.opengis.net/spec/iot_sensing/1.1/req/datamodel/feature-of-interest/relations

Test purpose

Check if each FeatureOfInterest entity has the mandatory properties and mandatory relations as defined in this specification.

Test method

Inspect the full JSON object of the FeatureOfInterest entity sets (i.e., without $select) to identify, if each entity has the mandatory properties defined in the corresponding requirement.

Inspect the full JSON object of each FeatureOfInterest entity set (i.e., without using the $select query option) to identify, if each entity has the mandatory relations (i.e., @iot.navigationLink) defined in the corresponding requirement.
A.1.10 Conformance class: SensorThings API Resource Path

Conformance class id:

http://www.opengis.net/spec/iot_sensing/1.1/conf/resource-path

Test: Resource Path

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/resource-path/resource-path-to-entities

Requirements

19. http://www.opengis.net/spec/iot_sensing/1.1/req/resource-path/resource-path-to-entities

Test purpose

Check if the service supports all the resource path usages as defined in the requirement http://www.opengis.net/spec/iot_sensing/1.1/req/resource-path/resource-path-to-entities.

Test method

Inspect the service to identify, if each resource path usage has been implemented property.

A.2. SensorThings API Filtering Extension Tests

This section contains the conformance classes for the SensorThings API filtering extension. That means a SensorThings API service that allows clients to further filter data with query options needs to pass the conformance tests defined in this section.

A.2.1 Conformance class: SensorThings API Request Data with Filters

Conformance class id:

http://www.opengis.net/spec/iot_sensing/1.1/conf/request-data

Dependencies:

  1. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/entity-control-information

  2. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/thing

  3. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/location

  4. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/historical-location

  5. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/datastream

  6. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/sensor

  7. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/observed-property

  8. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/observation

  9. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/feature-of-interest

  10. http://www.opengis.net/spec/iot_sensing/1.1/conf/resource-path

A.2.1.1 Test: Query Option Order

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/request-data/order

Requirements

22. http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/order

Test purpose

Check if the results of the service requests are as if the system query options were evaluated in the order as defined in this specification.

Test method

Send a query includes the query options listed in requirement http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/order, and check if the results are evaluated according to the order defined in this specification.

A.2.1.2 Test: Request Data with $expand and $select

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/request-data/expand-and-select

Requirements

23. http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/expand
24. http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/select

Test purpose

Check if the service supports $expand and $select as defined in this specification.

Test method

Send requests with $expand following the different usages as defined in the requirement http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/expand, check if the server returns appropriate result as defined in this specification.

Send requests with the $select option following the different usages as defined in the requirement http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/select, check if the server returns appropriate result as defined in this specification.

A.2.1.3 Test: Query Option Response Code

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/request-data/status-codes

Requirements

20. http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/status-code
21. http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/query-status-code

Test purpose

Check when a client requests an entity that is not available in the service, if the service responds with 404 Not Found or 410 Gone as defined in the requirement http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/status-code

Check when a client use a query option that doesn’t support by the service, if the service fails the request and responds with 501 NOT Implemented as defined in the requirement http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/query-status-code.

Test method

Send a HTTP request for an entity that is not available in the service, check if the server returns 404 Not Found or 410 Gone.

(If applicable) Send a query with a query option that is not supported by the service, check if the server returns 501 Not Implemented.

A.2.1.4 Test: Sorting Query Option

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/request-data/sorting

Requirements

25. http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/orderby

Test purpose

Check if the service supports the $orderby query option as defined in this specification.

Test method

Send a query with the $orderby query option, check if the server returns appropriate result as defined in this specification.

A.2.1.5 Test: Client-driven Pagination Query Option

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/request-data/client-driven-pagination

Requirements

26. http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/top 27. http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/skip 28. http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/count

Test purpose

Check if the service supports the $top, $skip and $count query option as defined in this specification.

Test method

Send a query with the $top query option, check if the server returns appropriate result as defined in this specification.

Send a query with the $skip query option, check if the server returns appropriate result as defined in this specification.

Send a query with the $count query option, check if the server returns appropriate result as defined in this specification.

A.2.1.6 Test: Filter Query Option

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/request-data/filter-query-options

Requirements

29. http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/filter 30. http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/built-in-filter-operations 31. http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/built-in-query-functions

Test purpose

Check if the service supports the $filter query option, the built-in filter operators, the built-in filter functions and implements the correct operator precedence as defined in this specification.

Test method

Send a query with the $filter query option, check if the server returns appropriate result as defined in this specification.

Send a query with the $filter query option for each built-in filter operator, check if the server returns appropriate result as defined in this specification.

Send a query with the $filter query option for each combination of two built-in filter operators with adjacent operator precedence, check if the server returns appropriate result as defined in this specification.

Send a query with the $filter query option for each built-in filter function, check if the server returns appropriate result as defined in this specification.

A.2.1.7 Test: Server-driven Pagination

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/request-data/server-driven-pagination

Requirements

32. http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/pagination

Test purpose

Check if the service supports the server-driven pagination as defined in the requirement http://www.opengis.net/spec/iot_sensing/1.1/req/request-data/pagination.

Test method

Send a query to list all entities of an entity set, check if the server returns a subset of the requested entities as defined in this specification.

A.3. SensorThings API Create-Update-Delete Extension Tests

This section contains the conformance classes for the SensorThings API create-update-delete extension. That means a SensorThings API service that allows clients to create/update/delete entities needs to pass the conformance tests defined in this section.

A.3.1 Conformance class: SensorThings API Create-Update-Delete

Conformance class id:

http://www.opengis.net/spec/iot_sensing/1.1/conf/create-update-delete

Dependencies:

  1. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/entity-control-information

  2. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/thing

  3. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/location

  4. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/historical-location

  5. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/datastream

  6. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/sensor

  7. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/observed-property

  8. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/observation

  9. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/feature-of-interest

  10. http://www.opengis.net/spec/iot_sensing/1.1/conf/resource-path

A.3.1.1 Test: Sensing Entity Creation

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/create-update-delete/sensing-entity-creation

Requirements

33. http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/create-entity

34. http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/link-to-existing-entities

35. http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/deep-insert

36. http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/deep-insert-status-code

8. http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/historical-location-auto-creation

Test purpose

Check if the service supports the creation of entities as defined in this specification.

Test method

For each SensorThings entity type creates an entity instance by following the integrity constraints of Table 24 and creating the related entities with a single request (i.e., deep insert), check if the entity instance is successfully created and the server responds as defined in this specification.

Create an entity instance and its related entities with a deep insert request that does not conform to the specification (e.g., missing a mandatory property), check if the service fails the request without creating any entity within the deep insert request and responds the appropriate HTTP status code.

For each SensorThings entity type issue an entity creation request that does not follow the integrity constraints of Table 24 with deep insert, check if the service fails the request without creating any entity within the deep insert request and responds the appropriate HTTP status code.

For each SensorThings entity type creates an entity instance by linking to existing entities with a single request, check if the server responds as defined in this specification.

For each SensorThings entity type creates an entity instance that does not follow the integrity constraints of Table 24 by linking to existing entities with a single request, check if the server responds as defined in this specification.

Create an Observation entity for a Datastream without any Observations and the Observation creation request does not create a new or linking to an existing FeatureOfInterest, check if the service creates a new FeatureOfInterest for the created Observation with the location property of the Thing’s Location entity.

Create an Observation entity for a Datastream that already has Observations and the Observation creation request does not create a new or linking to an existing FeatureOfInterest, check if the service automatically links the newly created Observation with an existing FeatureOfInterest whose location property is from the Thing’s Location entity.

Create an Observation entity and the Observation creation request does not include resultTime, check if the resultTime property is created with a null value.

Create a Location for a Thing entity, check if the Thing has a HistoricalLocation created by the service according to the Location entity.

A.3.1.2 Test: Sensing Entity Update

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/create-update-delete/update-entity

Requirements

37. http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/update-entity

Test purpose

Check if the service supports the update of entities as defined in this specification.

Test method

For each SensorThings entity type send an update request with PATCH, check (1) if the properties provided in the payload corresponding to updatable properties replace the value of the corresponding property in the entity and (2) if the missing properties of the containing entity or complex property are not directly altered.

(Where applicable) For each SensorThings entity type send an update request with PUT, check if the service responds as defined in Section 10.3.

For each SensorThings entity type send an update request with PATCH that contains related entities as inline content, check if the service fails the request and returns appropriate HTTP status code.

For each SensorThings entity type send an update request with PATCH that contains binding information for navigation properties, check if the service updates the navigationLink accordingly.

A.3.1.3 Test: Sensing Entity Deletion

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/create-update-delete/sensing-entity-deletion

Requirements

38. http://www.opengis.net/spec/iot_sensing/1.1/req/create-update-delete/delete-entity

Test purpose

Check if the service supports the deletion of entities as defined in Section 10.4.

Test method

Delete an entity instance, and check if the service responds as defined in Section 10.4.

A.4. SensorThings API Batch Request Extension Tests

This section contains the conformance classes for the SensorThings API batch request extension. That means a SensorThings API service that allows clients to send a single HTTP request that groups multiple requests needs to pass the conformance tests defined in this section.

A.4.1 Conformance class: SensorThings API Batch Request

Conformance class id:

http://www.opengis.net/spec/iot_sensing/1.1/conf/batch-request

Dependencies:

  1. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/entity-control-information

  2. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/thing

  3. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/location

  4. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/historical-location

  5. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/datastream

  6. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/sensor

  7. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/observed-property

  8. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/observation

  9. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/feature-of-interest

  10. http://www.opengis.net/spec/iot_sensing/1.1/conf/resource-path

A.4.1.1 Test: Batch Request

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/batch-request/batch-request

Requirements

39. http://www.opengis.net/spec/iot_sensing/1.1/req/batch-request/batch-request

Test purpose

Check if the service supports the batch request as defined in Chapter 11.

Test method

Submit batch requests according to the examples listed in Chapter 11, check if the service responds as defined in this specification.

A.5. SensorThings API MultipleDatastream Tests

This section contains the conformance classes for the SensorThings API MultiDatastream extension. That means a SensorThings API service that allows clients to group a collection of observations’ results into an array (i.e., a complex result type) needs to pass the conformance tests defined in this section.

A.5.1 Conformance class: SensorThings API MultiDatastream

Conformance class id:

http://www.opengis.net/spec/iot_sensing/1.1/conf/multi-datastream

Dependencies:

  1. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/entity-control-information

  2. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/thing

  3. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/location

  4. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/historical-location

  5. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/datastream

  6. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/sensor

  7. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/observed-property

  8. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/observation

  9. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/feature-of-interest

  10. http://www.opengis.net/spec/iot_sensing/1.1/conf/resource-path

A.5.1.1 Test: SensorThings API MultiDatastream

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/multi-datastream/multi-datastream-valid

Requirements

40. http://www.opengis.net/spec/iot_sensing/1.1/req/multi-datastream/properties

41. http://www.opengis.net/spec/iot_sensing/1.1/req/multi-datastream/relations

42. http://www.opengis.net/spec/iot_sensing/1.1/req/multi-datastream/constraints

Test purpose

Check if the service’s MultiDatastream entity has the mandatory properties and relations as defined in this specification.

Test method

Inspect the full JSON object of a MultiDatastream entity (i.e., without $select) to identify, if each entity has the mandatory properties and relations, and fulfill the constraints defined in the corresponding requirements.

A.6. SensorThings API Data Array Extension

This section contains the conformance classe for the SensorThings API data array extension. That means a SensorThings API service that allows clients to request the compact data array encoding defined in this specification needs to pass the conformance tests defined in this section.

A.6.1 Conformance class: SensorThings API Data Array

Conformance class id:

http://www.opengis.net/spec/iot_sensing/1.1/conf/data-array

Dependencies:

  1. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/entity-control-information

  2. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/thing

  3. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/location

  4. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/historical-location

  5. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/datastream

  6. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/sensor

  7. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/observed-property

  8. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/observation

  9. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/feature-of-interest

  10. http://www.opengis.net/spec/iot_sensing/1.1/conf/resource-path

A.6.1.1 Test: SensorThings API Sensing Data Array

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/data-array/data-array-valid

Requirements

43. http://www.opengis.net/spec/iot_sensing/1.1/req/data-array/data-array

Test purpose

Check if the service supports the data array extension as defined in Chapter 13.

Test method

Issue a GET request for Datastreams (and MultiDatastreams if applicable) that includes the query option "$resultFormat=dataArray", and then inspect the returned JSON to identify if it fulfills the data array format as defined in Chapter 13.

Create Observations for at least two Datastreams by using the data array format as defined in Chapter 13. Inspect the response code and returned JSON to identify if it fulfills the response as defined in Chapter 13.

A.7. SensorThings API Observation Creation via MQTT Extension Tests

This section contains the conformance class for the SensorThings API Observation creation extension. That means a SensorThings API service that allows clients to create Observations via MQTT needs to pass the conformance tests defined in this section.

A.7.1 Conformance class: SensorThings API Observation Creation via MQTT

Conformance class id:

http://www.opengis.net/spec/iot_sensing/1.1/conf/create-observations-via-mqtt

Dependencies:

  1. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/entity-control-information

  2. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/thing

  3. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/location

  4. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/historical-location

  5. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/datastream

  6. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/sensor

  7. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/observed-property

  8. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/observation

  9. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/feature-of-interest

  10. http://www.opengis.net/spec/iot_sensing/1.1/conf/resource-path

  11. http://www.opengis.net/spec/iot_sensing/1.1/conf/create-update-delete

A.7.1.1 Test: SensorThings API Observation Creation via MQTT

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/create-observations-via-mqtt/observation-creation

Requirements

44. http://www.opengis.net/spec/iot_sensing/1.1/req/create-observations-via-mqtt/observations-creation

Test purpose

Check if the service supports the creation and update of entities via MQTT as defined in Section 14.1.

Test method

Create an Observation entity instance containing binding information for navigation properties using MQTT Publish, check if the server responds as defined in Section 14.1.

A.8. SensorThings API Receiving Updates via MQTT Extension Tests

This section contains the conformance class for the SensorThings API receiving updates extension. That means a SensorThings API service that allows clients to receive notifications regarding updates of entities via MQTT needs to pass the conformance tests defined in this section.

A.8.1 Conformance class: SensorThings API Receiving Updates via MQTT

Conformance class id:

http://www.opengis.net/spec/iot_sensing/1.1/conf/receive-updates-via-mqtt

Dependencies:

  1. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/entity-control-information

  2. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/thing

  3. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/location

  4. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/historical-location

  5. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/datastream

  6. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/sensor

  7. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/observed-property

  8. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/observation

  9. http://www.opengis.net/spec/iot_sensing/1.1/conf/datamodel/feature-of-interest

  10. http://www.opengis.net/spec/iot_sensing/1.1/conf/resource-path

  11. http://www.opengis.net/spec/iot_sensing/1.1/conf/create-update-delete

A.8.1.1 Test: SensorThings API Receiving Updates via MQTT

Test id

http://www.opengis.net/spec/iot_sensing/1.1/conf/receive-updates-via-mqtt/receive-updates

Requirements

45. http://www.opengis.net/spec/iot_sensing/1.1/req/receive-updates-via-mqtt/receive-updates

Test purpose

Check if a client can receive notifications for the updates of a SensorThings entity set or an individual entity with MQTT.

Test method

Subscribe to an entity set with MQTT Subscribe. Then create a new entity of the subscribed entity set. Check if a complete JSON representation of the newly created entity through MQTT is received.

Subscribe to an entity set with MQTT Subscribe. Then update an existing entity of the subscribed entity set. Check if a complete JSON representation of the updated entity through MQTT is received.

Subscribe to an entity’s property with MQTT Subscribe. Then update the property with PATCH. Check if the JSON object of the updated property is received.

Subscribe to multiple properties of an entity set with MQTT Subscribe. Then create a new entity of the entity set. Check if a JSON object of the subscribed properties is received.

Subscribe to multiple properties of an entity set with MQTT Subscribe. Then update an existing entity of the entity set with PATCH. Check if a JSON object of the subscribed properties is received.

Annex B: Revision history

Date Release Author Paragraph modified Description

2018-10-12

1.1

Steve Liang

Many

Properties field is added to all the entities.

2018-10-15

1.1

Hylke van der Schaaf

9.3.3.5.2 Built-in query functions

Added three-parameter substring function.

2018-10-16

1.1

Hylke van der Schaaf

9.3.3.5.1. Built-in filter operations; A.2.1.6 Test: Filter Query Option

Specify operator precedence.

2018-12-07

1.1

Hylke van der Schaaf

9.3.3.1 $orderby

Removed reference to ordering by a "type cast".

2019-04-11

1.1

Hylke van der Schaaf

9.2.1 Usage 1: no resource path

Add serverSettings property in response of SERVICE_ROOT_URI requests.

2019-04-29

1.1

Brian Miles

10.4. Delete an entity

Add integrity contraint between Things and HistoricalLocations removal.

2019-04-29

1.1

Brian Miles

9.2.7. Usage 7: address to an associationLink

Fix inconsistencies in definition of @iot.selfLink property.

2019-05-02

1.1

Hylke van der Schaaf

8.2.3. HistoricalLocation

Location of a Thing can not be updated 'in the past'.

2019-08-01

1.1

Brian Miles

8.2.2. Location; 8.2.8 FeatureOfInterest

Update GeoJSON MIME type to application/geo+json.

2019-08-01

1.1

Brian Miles

8.2.2. Location

Correct the description of GeoJSON as using a 'geographic space model' rather then the more generic 'geometric space model'.

2019-08-01

1.1

Hylke van der Schaaf

14. SensorThings Sensing MQTT Extension

Add version prefix to MQTT topics.

2019-08-22

1.1

Hylke van der Schaaf

Many

Update version number in text and URIs from 1.0 to 1.1.

2019-08-22

1.1

Hylke van der Schaaf

13. SensorThings Data Array Extension

Explain query parameters when used with dataArray extension; Changed examples to use absolute navigation links; Add @iot.nextLink and @iot.count to the examples; Fixed wording of test method; Fixed incorrect relative navigation link; Removed unexplained dataArray@iot.count elements from examples.

2019-08-22

1.1

Hylke van der Schaaf

2. Conformance

Grouped data model related requirements and conformance classes into a datamodel class.

2019-09-09

1.1

Brian Miles

8.2.5. Sensor

Expand the Sensor encodingType with a ValueCode for webpages/URLs.

2019-10-22

1.1

Hylke van der Schaaf

11. Batch Requests

Clarified batch-processing referencing mechanisms; Remove example request headers: If-Match, Content-Transfer-Encoding.

2019-12-04

1.1

Hylke van der Schaaf

7.7. SensorThings API and Security

Added implications of conformance class list for security extensions.

2020-11-03

1.1

Hylke van der Schaaf

8.2. The Sensing Entities; 12. SensorThings MultiDatastream extension

Fixed images; HistoricalLocation → Thing relation name should be singular.

2020-11-11

1.1

Hylke van der Schaaf

9.3. Requesting Data

Corrected order of system query options; Expanded items are implicitly selected.

Annex C: Bibliography

[1]The GeoJSON Format Specification, January 15, 2015. Available Online: https://datatracker.ietf.org/doc/draft-butler-geojson/

[2]ITU-T Y.2060 Overview of the Internet of Things, 2012. Available Online:https://www.itu.int/rec/T-REC-Y.2060-201206-I

[3]OGC and ISO 19156:2001, OGC 10-004r3 and ISO 19156:2011(E), OGC Abstract Specification: Geographic information — Observations and Measurements. Available Online: http://portal.opengeospatial.org/files/?artifact_id=41579

[4]OGC 12-000, OGC® SensorML: Model and XML Encoding Standard. Available Online: http://www.opengeospatial.org/standards/sensorml

[5]RFC 5023, The Atom Publishing Protocol. Available Online: https://www.ietf.org/rfc/rfc5023.txt

[6]RFC 6902, JavaScript Object Notation (JSON) Patch. Available Online:https://www.ietf.org/rfc/rfc6902.txt

[1]www.opengeospatial.org/cite

[2]The two terms of IoT and WoT are frequently used interchangeably.

[3]In some cases, the Sensor in this data model can also be seen as the Procedure (method, algorithm, or instrument) defined in [OGC 10-004r3 and ISO 19156:2011].