The OGC CF-netCDF data model supports multi-dimensional gridded data and multi-dimensional multi-point data, representing space and time-varying phenomena. In particular, this extension standard is limited to multi-point, and regular and warped grids.

This standard specifies the CF-netCDF data model encoding using the OGC GML 3.2.1 coverage application schema, as well as CF-netCDF data exchange format and protocol encoding.

This standard specifies: (a) the CF-netCDF GML encoding to be used by OGC standards; (b) the CF-netCDF data format exchanged using OGC standards; (c) the Internet protocol characteristics to effectively exchange CF-netCDF data.

As per the GML 3.3. standard, GML 3.3 imports the 3.2 schema. The canonical location of the 3.2 all components schema document for 3.3 is http://schemas.opengis.net/gml/3.2.1/gml.xsd

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

ogcdoc, netcdf, cf-netcf, encoding extension, multi-dimensional, gml, data format.

This standard describes an extension of the CF-netCDF 3.0 data model [OGC 11-165r02].

This extension is required to encode CF-netCDF 3.0 datasets using the “OGC Implementation Schema for Coverages” specification [OGC 09-146r2] and to exchange CF-netCDF datasets.

Suggested additions, changes, and comments on this draft standard are welcome and encouraged. Such suggestions may be submitted by email message or by making suggested changes in an edited copy of this document.

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.

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

The University Corporation for Atmospheric Research (UCAR);

The Italian National Research Council, Institute of Atmospheric Pollution Research (CNR-IIA, Florence Dept.).

All questions regarding this submission should be directed to the editor or the submitters.

1          Scope

This document specifies the CF-netCDF model encoding using the GML 3.2.1 Application Schema –Coverage entities. Besides, it specifies the data format and Internet protocol characteristics to serve CF-netCDF data in an effective and usable way.

GML 3.2.1 has not been deprecated. As per the GML 3.3. standard, GML 3.3 imports the 3.2 schema. The canonical location of the 3.2 all components schema document for 3.3 is http://schemas.opengis.net/gml/3.2.1/gml.xsd.

This CF-netCDF 3.0 extension allows discovery and access services to exchange CF-netCDF data –e.g. encoded in GML. In fact, this specification introduces a set of requirements which a WxS implementation must fulfil to describe and exchange CF-netCDF 3.0 datasets from server to client using the coverage extension of the GML 3.2.1 encoding format.

This standard specifies: (a) the CF-netCDF GML encoding to be used by OGC standards; (b) the CF-netCDF data format exchanged using OGC standards; (c) the Internet protocol characteristics to effectively exchange CF-netCDF data.

CF-netCDF encoding format is netCDF conforming to the Climate and Forecast (CF) conventions (CF-netCDF). It consists of either a binary, XML, or ASCII format which encodes the CF-netCDF data model.

CF-netCDF 3.0 has emerged as a well-supported data model and encoding for several different domains, including: atmospheric science, oceanography, climatology, meteorology, hydrology, etc.

This specification deals with multi-dimensional discrete coverage data and multi-dimensional multi-point data.

2          Conformance

Standardization target is the encoding of netCDF-CF datasets returned by any WxS implementation (currently: servers).

In particular, this standard defines three standardization targets: (a) CF-netCDF GML implementations (currently encodings); (b) CF-netCDF data format (currently encodings); (c) CF-netCDF data format (currently encodings) returned by multiple part messages.

This document establishes three requirements classes, one for each standardization target:

1.     CF-netCDF-1.6 GML encoding, of  http://www.opengis.net/spec/netCDF_data-model/req/CF-netCDF-1.6-GML-encoding -for the standardization target (a);

2.     CF-netCDF-1.6 data format, of    http://www.opengis.net/spec/netCDF_data-model/req/CF-netCDF-1.6-Data-format -for the standardization target (b);

3.     CF-netCDF-1.6 multipart data encoding, of    http://www.opengis.net/spec/netCDF_data-model/req/CF-netCDF-1.6-Multipart-encoding -for the standardization target (c);

and three corresponding pertaining conformance class, CF-netCDF-1.6, with URIs:

1.     http://www.opengis.net/spec/netCDF_data-model/conf/CF-netCDF-1.6-GML-encoding

2.     http://www.opengis.net/spec/netCDF_data-model/conf/CF-netCDF-1.6-Data-format

3.     http://www.opengis.net/spec/netCDF_data-model/req/CF-netCDF-1.6-Multipart-encoding

Requirements and conformance test URIs defined in this document are relative to http://www.opengis.net/spec/netCDF_data-model/.

Annex A lists the conformance tests which shall be exercised on any software artifact claiming to implement an CF-netCDF 3.0 extension for GML 3.2.1 encoding.

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.

OGC 10-090, NetCDF Core version 1.0

Conformance classes used:
•       core

OGC 10-092, NetCDF Binary Encoding Extension Standard: NetCDF Classic and 64-bit Offset Format  version 1.0

Conformance classes used:
•       netCDF classic
•       netCDF 64-bit

OGC 11-165r2, CF-netCDF Data Model extension specification, version 2.0.1

Conformance classes used:
•       CF-netCDF  core
•       CF-netCDF Discrete Sampling
•       CF-netCDF Mapping onto ISO 19123

OGC 07-036, Geography Markup Language (GML) Encoding Standard, version 3.2.1

Conformance classes used:
•      GML writing

OGC 09-146r1, OGC^® Implementation Schema for Coverages, version 1.0

Conformance classes used:
•       gml-coverage

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 Coverage

Feature that acts as a function to return values from its range for any direct position within its spatiotemporal domain [OGC 07-111]

4.2 Data Model

A description of the organization of data in a manner that reflects an information structure [ISO/IEC 11179-1 Specification and standardization of data elements – Part 1: Framework]

NOTE: netCDF literature reports the following definition for data model: a way of thinking about scientific data by applying a data model theory. It is an abstraction that describes how datasets are represented and used. In computer terms, a data model can be thought of as equivalent to an abstract object model in Object Oriented Programming in that an abstract data model describes data objects and what methods can be used on them.

4.3 Feature

abstraction of real world phenomena [5].

NOTE A feature may occur as a type or an instance.

4.4 GMLCOV

Note that OGC Coverage Implementation Schema 1.1 supersedes its predecessor version, GML 3.2.1 Application Schema – Coverages version 1.0.1, nicknamed GMLCOV, in a backwards compatible way. Instead of naming the new version GMLCOV 1.1, the standard has been renamed to Coverage Implementation Schema (CIS) 1.1 to remedy misunderstandings caused by the initial title, such as that only a GML encoding is defined here (whereas in fact a format-independent implementable coverage model is established).

For simplicity, the GMLCOV shorthand is used throughout this specification.

4.5 Grid

Network composed of two or more sets of curves in which the members of each set intersect the members of the other sets in a algorithmic way [5]

NOTE: the curves partition a space into grid cells.

4.6 MIME

MIME (Multi-Purpose Internet Mail Extensions) is an extension of the original Internet e-mail protocol that lets people use the protocol to exchange different kinds of data files on the Internet: audio, video, images, application programs, and other kinds, as well as the ASCII text handled in the original protocol, the Simple Mail Transfer Protocol (SMTP).

4.7 Multipart messages

Through the use of the multipart type, MIME allows mail messages to have parts arranged in a tree structure where the leaf nodes are any non-multipart content type and the non-leaf nodes are any of a variety of multipart types.

4.8 Multi-point coverage

A discrete coverage which is characterized by a finite domain consisting of points. Generally, the domain is a set of irregularly distributed points.

A set of hydrographic soundings is an example of a discrete point coverage.

4.9 NetCDF

NetCDF is a standard for data on complex grids –curvilinear in XY; sigma and density-related in Z; climatological and artificial calendars in T; and heading towards “tile mosaics” and 5D forecast ensembles in the near future.

4.10 Web address

For purposes of this document, Web address is an HTTP URL that allows applications to access remote (optionally, time-aggregated collections of) netCDF-CF files (virtual datasets – often terabyte sized) through netCDF API –as if they were local netCDF files.

5          Conventions

5.1           Namespace prefix conventions

The following namespaces are used in this document. The prefix abbreviations used constitute conventions used here, but are notnormative. The namespaces to which the prefixes refer are normative, however.

5.2           CF-netCDF data model

This document does not contain inline a formal specification of the CF-netCDF data model. In fact, it is available as an OGC specification [OGC 11-165r2]. This specification formalizes the CF-netCDF data model mapping onto the ISO 19123 coverage geometry model.

For reader’s convenience, the CF-netCDF data model is shown in Figure 1, Figure 2, and Figure 3. An example of CF-netCDF dataset is reported in the Annex B.

5.3           Web address

For the scope of this document, a Web address is a transparent mechanism by which an application can use netCDF API calls on a remote file. Thus, for any netCDF subset that may be derived from a WxS server, there may be a Web URL that is an indirect reference to that same subset.

Essentially, the netCDF file is just a de-referencing of this URL. Any application program that can utilize a netCDF file can (in principal) utilize the URL equivalently.

NetCDF Community applications commonly make use of Web addresses (i.e. HTTP URLs) to access remote (optionally, time-aggregated collections of) netCDF-CF files (virtual datasets – often terabyte sized) through netCDF API –as if they were local netCDF files.

6          CF-NetCDF dataset encoding with GML 3.2.1 – application schema – Coverages

GML 3.2.1 Application Schema -Coverage data model [OGC 09-146r1] introduces the concept of Coverage (i.e. GMLCOV:Coverage). For the reader’s convenience the data model is depicted in Figure 4 and Figure 5.

The related GML:DomainSet and GML:RangeSet entities are defined in [7]; while, SWE Common:DataRecord is defined in [8].

6.1           GML 3.2.1 Coverage types

Since CF-netCDF dataset realizes the ISO19123:CV_DiscreteCoverage type [4], the following GML 3.2.1 coverage types are considered for the mapping (see Figure 4): GMLCOV:GridCoverage type, GMLCOV:RectifiedGridCoverage type, GMLCOV:ReferenceableGridCoverage type, or GMLCOV:MultiPointCoverage –i.e. ISO 19123:CV_DiscretePointCoverage.

6.2           Encoding rules for CF-netCDF dataset

Considering the mapping between the GMLCOV:Coverage object and property names to the corresponding class names and their attributes in ISO 19123 (see Table D.8 of [7] and the constraints introduced by [OGC 09-146r1]), and the mapping between the CF-netCDF dataset object and property names to the corresponding class names and their attributes in ISO 19123 (see OGC 11-165r2 [4]), Table 1 defines the mapping between the CF-netCDF dataset object and property names to the corresponding GMLCOV:Coverage object and property names. Figure 6 and Figure 7 depict these mapping rules.

6.3           Encoding rules for CF-Variables

6.4           Encoding rules for CF-netCDF CoordinateSystem

6.5           Encoding rules for CF-netCDF DiscreteSamplingGeometry

7          Service operation response returning a CF-netCDF dataset

7.1           Concrete coverage types

For WxS, the GML encoding is generally used for the purpose of defining response semantics. A server may deliver a result dataset in some other format –e.g. CF-netCDF. However, it is required that result datasets, regardless of what the encoding chosen is, have a content which is consistent with the GML specification [OGC 09-146r1].

7.2           Concrete CF-netCDF data format

The schema depicted in Figure 8 introduces the concrete CF-netCDF data format used to return requested datasets.

7.3           GridCoverageFile class

The response to a successful operation requesting a CF-netCDF dataset is a concrete sub-type of GMLCOV:Coverage which is encoded as a GridCoverageFile, an abstract entity which has three valuation subclasses: BinaryFile, XMLDocument, and Web address.

NOTE: a CF-netCDF BinaryFile may be accessed directly or can be referenced by: (a) an XMLDocument object (e.g. an ncML dataset); (b) an Web address object.

7.4           BinaryFile class

BinaryFile class has two concrete sub-types: CF-netCDF-File and CF-netCDF-64bit-File. They represent a netCDF ver. 3.0 binary file, complying with the CF ver. 1.1 conventions. These binary encodings are based on the “OGC NetCDF Binary Encoding Extension Standard: NetCDF Classic and 64-bit Offset Format” [9].

MIME type string used to refer to CF-netCDF binary encoding is:

application/CF-netCDF

Note: the only MIME type in use presently is “application/x-netcdf” and it is not officially registered.  Thus, the MIME types discussed below are new and application for registration will be made to IANA.

7.5           XMLDataset class

XMLDataset class has three concrete sub-types: NcML-Dataset, GML-3.2.1-Coverage, and NcML-G-Dataset.

7.5.1     NcML-Dataset

NcML-Dataset represents a ncML ver. 1.0 document [10]. A ncML document provides the XML encoding of one or more CF-netCDF files. For performances sake, a ncML document generally encodes only the CF-netCDF coverage metadata leaving the data values in the binary format and providing pointers (i.e. references) to those.

A ncML document may point to data values: (a) directly –i.e. referencing a CF-netCDF binary file; (b) including an Web address (i.e. HTTP URL)–which in turn reference a CF-netCDF file.

MIME type string used to refer to ncML-G dataset encoding is:

application/ncML+xml

This xml media type is still unregistered.

7.5.2     GML-3.2.1-Coverage

GML-3.2.1-Coveragerepresents the GML-based coverage encoding as specified by [OGC 09-146r1]. Such a document is generated applying the requirements contained in clause 6 and summarized in Table 1, Table 2, and Table 3.

MIME type string used to refer to GML coverage encoding is [OGC 09-144r1]:

application/gml+xml

7.5.3     NCML-G-Dataset

NcML-G-Datasetrepresents a ncML-G ver. 1.0 document [10]. A ncML-G document extends a ncML-Dataset by including a GML Coverage element generated from the ncML dataset itself. In fact, this language was conceived to explicitly encode the two data models mapping. This may be very useful to fully support both GIS and netCDF applications.

MIME type string used to refer to ncML-G dataset encoding is:

application/ncML+xml

This xml media type is still unregistered.

7.6           Web address class

This class realizes a well-adopted online reference to a CF-netCDF file. In fact, Web address is a relatively simple approach (i.e. an HTTP URL) that allows applications to access remote (optionally, time-aggregated collections of) netCDF-CF files (virtual datasets –often terabyte sized) through netCDF API –as if they were local netCDF files.

A Web address may also be contained by any concrete XMLDataset object to reference a CF-netCDF binary file.

Web address may be encoded using one of the following options: i) a specific MIME type for a well-known address syntax; ii) an HTML document containing a HTTP URL; iii) a simple text –semantically, this is a very dull solution, and is deprecated. 

NOTE: Result coverages, regardless of what the encoding chosen is, have a contents which is consistent with the GMLCOV:Coverage specification –see clause 6 and Table 1, Table 2, and Table 3.

7.7           WxS operation response: ncML-Dataset document structure

The netCDF community makes use of ncML to encode complex netCDF data structures. In fact, it is possible to use ncML elements to define a virtual netCDF dataset which consists of one or more netCDF data files.

In a service operation response returning a ncML document, the discrete coverage values are encoded and returned according to one or more of the following options:

         (i)     XML encoded values conforming to the ncML schema: this ncML section encodes the content of a CF-netCDF binary file.

       (ii)     CF-NetCDF binary files (i.e. BinaryFile objects) attached to an ncML document.

      (iii)     Web address encoded in the ncML schema: actually, this ncML section references the content of a CF-netCDF binary file.

In any case, the coverage metadata section is encoded in the ncML document as elements conforming to the ncML schema.

For instance, Figure 9 depicts a complex ncML-Dataset (and optionally ncML-G-Dataset) structure transferred as a successful WxS operation response.

This type of encoding allows to return very complex data packages. As to the considered example, the returned coverage (i.e. dataset) values are encoded as: (a) two ncML DataBlocks elements (encoding values defined in a couple of CF-netCDF binary files); (b) a Web address pointing to the values defined in a third CF-netCDF file; (c) binary attachments –i.e. the data values defined in a fourth and fifth CF-netCDF binary file enclosed as ncML binary attachments.

For ncML-Dataset, coverage metadata are encoded as ncML elements. Besides, the ncML-G-Dataset extension adds a related grid coverage description using the GML elements (see Figure 9); thus, the metadata elements mapping is explicitly reported.

8          WxS operation response message: Multipart data encoding

Multipart data encoding is a technique for transferring multiple contents inside a single HTTP (or HTTPS) Response. In the context of WxS operation response it can be adopted whenever a binary content must be transferred.

Different strategies should be adopted for the different possible protocol bindings and encoding formats. Table 5 shows the two possibilities:

The WxS operation response can be encoded in a Multipart message. The encoding strategy is different depending on the use of SOAP or HTTP binding.

For multipart encoding of ncML-Dataset in SOAP responses, the MTOM-XOP specification is adopted according to the OGC “Web Services Common Standard” (OGC 06-121r9).

For multipart encoding of ncML-Dataset in HTTP responses the MIME Multipart/related standard is adopted.

8.1           Case #1and #2: SOAP or HTTP Response  returning ncML data

In case of ncML data the response can refer to a local or remote document. Local resources are always attached to the message, while remote resources can be attached as a copy to avoid multiple access. The HTTP or SOAP response must be encoded along with its attachments in a MIME Multipart/Related message using the rules described in Table 5. At least one multipart section will contain XML data instead of binary data.

An ncML dataset include either coverage data values or a pointer to them –i.e. a pointer to one or more netCDF binary files.

Therefore, returned ncML documents may directly encode coverage data values or point to one or more netCDF binary files. Example B.3.3 shows a response returning an ncML document which points to a netCDF binary file, which is included in the MIME Multipart/Related message. Both ncML and netCDF binary are remote resources referred by the SOAP document.

Examples B.3.1 and B.3.2 describe responses returning ncML documents which encode coverage data values.

Example B.3.3: SOAP Response returning  an ncML document referring a netCDF binary file included in the message.

 
  MIME-Version: 1.0
  Content-Type:
  multipart/related;
  boundary="----=_NextPart_000_0000_93251752.3C5526C0"
  
  ------=_NextPart_000_0000_93251752.3C5526C0
  Content-Type:
  application/xml; charset="UTF-8"
  
  <?xml
  version="1.0" encoding="UTF-8"?>
  <soap:Envelope
  xmlns:soap="http://www.w3.org/2001/12/soap-envelope">
    <soap:Header/>
    <soap:Body>
      <Coverages
  xmlns="http://www.opengis.net/wcs/1.1/ows"
  xmlns:ows="http://www.opengis.net/ows"
  xmlns:xlink="http://www.w3.org/1999/xlink"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:schemaLocation="http://www.opengis.net/wcs/1.1/ows ../owsCoverages.xsd
  http://www.opengis.net/ows ../../../ows/1.0.0/ows19115subset.xsd">
        <Coverage>
         
  <ows:Title>Example</ows:Title>
          <ows:Abstract>Example of
  coverage</ows:Abstract>
         
  <Identifier>Example</Identifier>
          <Reference
  href="cid:bfa8e8ac@example.net" />
          <Reference
  href="http://example.net/data/CoverageDataValues.nc" />
          <Reference
  href="http://example.net/data/Dataset.ncml" />
        </Coverage>
      </Coverages>
    </soap:Body>
  </soap:Envelope>
  ------=_NextPart_000_0000_93251752.3C5526C0
  Content-Type: application/xml
  Content-ID:
  <bfa8e8ac@example.net>
  
  ...(metadata content)...
  ------=_NextPart_000_0000_93251752.3C5526C0
  Content-Type:
  application/CF-netCDF
  Content-Transfer-Encoding:
  base64
  Content-ID: <c3499c27@example.net>
  Content-Location:
  http://example.net/data/CoverageDataValues.nc……
  ...(netCDF binary data
  content, pointed by the ncML dataset)...
  ------=_NextPart_000_0000_93251752.3C5526C0
  Content-Type:
  application/ncML+xml 
  Content-Transfer-Encoding:
  base64
  Content-ID:
  <1324bc12@example.net>
  Content-Location:
  http://example.net/data/Dataset.ncml
  …..
  ...( ncML dataset
  content)...
  ------=_NextPart_000_0000_93251752.3C5526C0--
  

NcML documents may contain coverage data values encoded as binary sections in base64 encoding. They can be left enclosed in the ncML document or, for efficiency purposes, they can be extracted and encoded in a format other than base64. Such improvement can be obtained serializing the ncML values element using nested multipart messages according to the MTOM/XOP specifications.

The following two encoding examples report multipart sections for ncML with binary data included and extracted using XOP, respectively.

8.1.1      Binary data included

Example 8.1.1: Response excerpt showing a ncML dataset containing coverage data values encoded as a binary section in base64 encoding.

  
  multipart section containing a ncML dataset with binary data 
      included (section outlined by a pale blue background)
  
  
------=_NextPart_000_0000_93251752.3C5526C0
Content-Type:
application/CF-netCDF
Content-ID:
<1324bc12@example.net>
Content-Location:
http://example.net/data/data2.ncml
 
<?xml version="1.0" encoding="UTF-8"?>
<netcdf xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     
  xmlns="http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2">
      <dimension name="longitude" length="96"/>
      <dimension name="bounds_axis" length="2"/>
      <dimension name="latitude" length="73"/>
      <dimension name="air_pressure" length="15"/>
      <dimension name="time" length="140"/>
      <attribute name="Conventions" type="string" value="CF-1.1"/>
      <attribute name="source" type="string" value="Data from model run ABC123"/>
      <variable name="longitude" shape="longitude" type="double">
          <attribute name="standard_name" type="string" value="longitude"/>
          <attribute name="units" type="string" value="degrees_east"/>
          <attribute name="bounds" type="string" value="bound_longitude"/>
         
  <attribute name="axis" type="string" value="X"/>
          <values increment="3.75" npts="96" start="0.0"/>
      </variable>
      <variable name="bound_longitude" shape="longitude bounds_axis" type="double"> </variable>
      <variable name="latitude" shape="latitude" type="double">
          <attribute name="standard_name" type="string" value="latitude"/>
          <attribute name="units" type="string" value="degrees_north"/>
          <attribute name="bounds" type="string" value="bound_latitude"/>
          <attribute name="axis" type="string" value="Y"/>
          <values increment="-2.5" npts="73" start="90.0"/>
      </variable>
      <variable name="bound_latitude" shape="latitude bounds_axis" type="double"> </variable>
      <variable name="air_pressure" shape="air_pressure" type="float">
          <attribute name="standard_name" type="string" value="air_pressure"/>
          <attribute name="units" type="string" value="hPa"/>
          <attribute name="axis" type="string" value="Z"/>
          <attribute name="positive" type="string" value="down"/>
          <values increment="70.71429" npts="15" start="10.0"/>
      </variable>
      <variable name="time" shape="time" type="double">
          <attribute name="calendar" type="string" value="360_day"/>
          <attribute name="standard_name" type="string" value="time"/>
          <attribute name="units" type="string" value="days since 2289-1-1"/>
          <attribute name="bounds" type="string" value="bound_time"/>
          <attribute name="axis" type="string" value="T"/>
          <values increment="360.0" npts="140" start="510.0"/>
      </variable>
      <variable name="bound_time" shape="time bounds_axis" type="double">
  </variable>
      <variable name="air_temperature" shape="time air_pressure latitude longitude" type="float">
          <attribute name="standard_name" type="string" value="air_temperature"/>
          <attribute name="units" type="string" value="Kir_temperature"/>
          <attribute name="long_name" type="string" value="temperature on pressure level"/>
         
  <attribute name="cell_methods" type="string" value="longitude: latitude: mean time: mean (interval: 4 h)"/>
          <attribute name="_FillValue" type="float" value="-1.073742e+09"/>
          <values
  xm:xmlmime="binary/octet-stream">Li4uKGJhc2U2NCBlbmNvZGVkIGRhdGEpLi4u...(base64
  encoded data)...BlbmNvZGVkIGRhdGEpLi4u==</values>
      </variable>
  </netcdf>
  ------=_NextPart_000_0000_93251752.3C5526C0--
  

8.1.2      Binary extracted using XOP

Example 8.1.2: HTTP Multipart/Related response showing a ncML dataset containing coverage data values extracted and encoded in a format other than base64 by serializing the <values> element using nested multipart messages according to the MTOM/XOP specifications.

multipart section containing a ncML
  dataset with binary data extracted using XOP 
  (section outlined by a pale blue background)
  

  ------=_NextPart_000_0000_93251752.3C5526C0
  MIME-Version: 1.0
  Content-Type:
  Multipart/Related;boundary=MIME_boundary; 
  type="application/xop+xml";
      start="<12dea45c@example.net >";
      startinfo="application/ncML+xml”; 
   
  --MIME_boundary
  Content-Type: application/xop+xml; charset=UTF-8; 
     
  type="application/ncML+xml; action=\"ProcessData\""
  Content-ID: <12dea45c@example.net>
  Content-Location: http://example.net/data/data2.ncml
   
  <?xml version="1.0" encoding="UTF-8"?>
  <netcdf
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     
  xmlns="http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2">
      <dimension name="longitude" length="96"/>
      <dimension name="bounds_axis" length="2"/>
      <dimension name="latitude" length="73"/>
      <dimension name="air_pressure" length="15"/>
     
  <dimension name="time" length="140"/>
      <attribute name="Conventions" type="string" value="CF-1.1"/>
      <attribute name="source" type="string" value="Data from model run ABC123"/>
      <variable name="longitude" shape="longitude" type="double">
          <attribute name="standard_name" type="string" value="longitude"/>
          <attribute name="units" type="string" value="degrees_east"/>
          <attribute name="bounds" type="string" value="bound_longitude"/>
          <attribute name="axis" type="string" value="X"/>
          <values increment="3.75" npts="96" start="0.0"/>
      </variable>
      <variable name="bound_longitude" shape="longitude bounds_axis" type="double"> </variable>
      <variable name="latitude" shape="latitude" type="double">
          <attribute name="standard_name" type="string" value="latitude"/>
          <attribute name="units" type="string" value="degrees_north"/>
          <attribute name="bounds" type="string" value="bound_latitude"/>
          <attribute name="axis" type="string" value="Y"/>
          <values increment="-2.5" npts="73" start="90.0"/>
      </variable>
      <variable name="bound_latitude" shape="latitude bounds_axis" type="double"> </variable>
      <variable name="air_pressure" shape="air_pressure" type="float">
          <attribute name="standard_name" type="string" value="air_pressure"/>
          <attribute name="units" type="string" value="hPa"/>
          <attribute name="axis" type="string" value="Z"/>
          <attribute name="positive" type="string" value="down"/>
          <values increment="70.71429" npts="15" start="10.0"/>
      </variable>
      <variable name="time" shape="time" type="double">
          <attribute name="calendar" type="string" value="360_day"/>
          <attribute name="standard_name" type="string" value="time"/>
          <attribute name="units" type="string" value="days since 2289-1-1"/>
          <attribute name="bounds" type="string" value="bound_time"/>
          <attribute name="axis" type="string" value="T"/>
          <values increment="360.0" npts="140" start="510.0"/>
  </variable>
      <variable name="bound_time" shape="time bounds_axis" type="double">
  </variable>
      <variable name="air_temperature" shape="time air_pressure latitude longitude" type="float">
          <attribute name="standard_name" type="string" value="air_temperature"/>
          <attribute name="units" type="string" value="Kir_temperature"/>
          <attribute name="long_name" type="string" value="temperature on pressure level"/>
          <attribute name="cell_methods" type="string" value="longitude: latitude: mean time: mean (interval: 4 h)"/>
          <attribute name="_FillValue" type="float" value="-1.073742e+09"/>
          <values xm:xmlmime="binary/octet-stream"><xop:Include 
     
  xmlns:xop='http://www.w3.org/2004/08/xop/include' 
      href='cid:bd43gh2y@example.net'/>
          </values>
      </variable>
  </netcdf>
  --MIME_boundary
  Content-Type:
  application/octet-stream
  Content-Transfer-Encoding:
  binary
  Content-ID:
  <bd43gh2y@example.net>
  ….
  ...(binary encoded data)...  
  --MIME_boundary--
  ------=_NextPart_000_0000_93251752.3C5526C0--
 

8.2           Content-ID generation

The RFC 2045 and RFC 2046 describe the use of the Content-ID header to identify the different sections of a multipart message. It allows cross-reference of sections, but since it is not required for all the usages, it is specified as optional. In some cases the Content-Location header can be used for the same objective. For netCDF datasets the cross-reference between sections (e.g. between metadata and binary section) is required, therefore the presence of the Content-ID is considered mandatory.

According to [RFC 2045]  “Content-ID values must be generated to be  world-unique”. In WxS operation responses it is suggested that Content-ID has the following format:

Content-ID : = Local “@” Domain

where Local is a locally unique identifier and Domain is an Internet domain administered by the coverages provider. The domain names assignment process assures the unicity. The locally unique identifier is opaque, meaning that no semantics is associated to the local name. For example it could be generated with a hashing function from coverages metadata.

8.3           OWS Common Manifest

According to the OGC “Web Services Common Standard” (OGC 06-121r9), if the coverage dataset is provided with a Manifest the message can be encoded as Multipart/Related. In such case the manifest is in the root part, while the netCDF coverage is encoded in other sections. Exploiting the recursive structure of multipart messages, the netCDF sections can be structured as explained above in SOAP or HTTP multipart sub-messages.

Annex : Conformance Class Abstract Test Suite (Normative)

A CF-netCDF 3.0 encoding using GML 3.2.1 Coverage application schema must satisfy the following system characteristics to be conformant with this specification.

A.1     Conformance Test Classes: CF-netCDF-1.6

This document establishes three conformance classes CF-netCDF ver 1.6 GML encoding instance, with URIs:

1.     http://www.opengis.net/spec/netCDF_data-model/conf/CF-netCDF-1.6-GML-encoding

2.     http://www.opengis.net/spec/netCDF_data-model/conf/CF-netCDF-1.6-Data-format

3.     http://www.opengis.net/spec/netCDF_data-model/req/CF-netCDF-1.6-Multipart-encoding

A.2     CF-netCDF-1.6-GML-encoding conformance class

This is the GML encoding conformance class for this standard.

There is a dependency on: CF-netCDF Data Model extension specification (OGC 11-165r2), Geography Markup Language (GML) Encoding Standard, version 3.2.1 (OGC 07-036), and OGC^® GML Application Schema for Coverages (OGC 09-146r1)

The following clauses relate to the conformance class identified with the URI: http://www.opengis.net/spec/netCDF_data-model/conf/CF-netCDF-1.6-GML-encoding

A.3     CF-netCDF-1.6-Data-format conformance class

This is the data format conformance class for this standard.

There is a dependency on the GML encoding conformance class of this standard (see A.2).

The following clauses relate to the conformance class identified with the URI: http://www.opengis.net/spec/netCDF_data-model/conf/CF-netCDF-1.6-Data-format

A.4     CF-netCDF-1.6-Multipart-encoding conformance class

This is the multipart data encodingconformance class for this standard.

There is a dependency on the data formatconformance class of this standard (see A.3).

The following clauses relate to the conformance class identified with the URI: http://www.opengis.net/spec/netCDF_data-model/req/CF-netCDF-1.6-Multipart-encoding

Annex : Examples (informative)

The following paragraphs collect the examples used and explained throughout the document.

B.1.                 Example: netCDF ver. 3 with CF1.1 convention dataset

netcdf air_temperature {
dimensions:
            longitude = 96 ;
            bounds_axis = 2 ;
            latitude = 73 ;
            air_pressure = 15 ;
            time = 140 ;
variables:
            double longitude(longitude) ;
                        longitude:standard_name = “longitude” ;
                        longitude:units = “degrees_east” ;
                        longitude:bounds = “bound_longitude” ;
                        longitude:axis = “X” ;
                        double bound_longitude(longitude, bounds_axis) ;
            double latitude(latitude) ;
                        latitude:standard_name = “latitude” ;
                        latitude:units = “degrees_north” ;
                        latitude:bounds = “bound_latitude” ;
                        latitude:axis = “Y” ;
                        double bound_latitude(latitude, bounds_axis) ;
            float air_pressure(air_pressure) ;
                        air_pressure:standard_name = “air_pressure” ;
                        air_pressure:units = “hPa” ;
                        air_pressure:axis = “Z” ;
                        air_pressure:positive = “down” ;
            double time(time) ;
                        time:calendar = “360_day” ;
                        time:standard_name = “time” ;
                        time:units = “days since 2289-1-1” ;
                        time:bounds = “bound_time” ;
                        time:axis = “T” ;
                        double bound_time(time, bounds_axis) ;
            float air_temperature(time, air_pressure, latitude, longitude) ;
                        air_temperature:standard_name = “air_temperature” ;
                        air_temperature:units = “K” ;
                        air_temperature:long_name = “temperature on pressure levels” ;
                        air_temperature:cell_methods = “longitude: latitude: mean time: mean (interval: 4 h)” ;
                        air_temperature:_FillValue = -1.073742e+09f ;
                       
// global attributes:
                        :Conventions = “CF-1.1” ;
                        :source = “Data from model run ABC123” ;
data:
 
 longitude = 0, 3.75, 7.5, 11.25, 15, 18.75, 22.5, 26.25, 30, 33.75, 37.5,
    41.25, 45, 48.75, 52.5, 56.25, 60, 63.75, 67.5, 71.25, 75, 78.75, 82.5,
    86.25, 90, 93.75, 97.5, 101.25, 105, 108.75, 112.5, 116.25, 120, 123.75,
    127.5, 131.25, 135, 138.75, 142.5, 146.25, 150, 153.75, 157.5, 161.25,
    165, 168.75, 172.5, 176.25, 180, 183.75, 187.5, 191.25, 195, 198.75,
    202.5, 206.25, 210, 213.75, 217.5, 221.25, 225, 228.75, 232.5, 236.25,
    240, 243.75, 247.5, 251.25, 255, 258.75, 262.5, 266.25, 270, 273.75,
    277.5, 281.25, 285, 288.75, 292.5, 296.25, 300, 303.75, 307.5, 311.25,
    315, 318.75, 322.5, 326.25, 330, 333.75, 337.5, 341.25, 345, 348.75,
    352.5, 356.25 ;

B.2.                 Example for an ncML dataset

<?xml version=“1.0” encoding=“UTF-8”?>
<netcdf xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2">
    <dimension name=“longitude” length=“96”/>
    <dimension name=“bounds_axis” length=“2”/>
    <dimension name=“latitude” length=“73”/>
    <dimension name=“air_pressure” length=“15”/>
    <dimension name=“time” length=“140”/>
    <attribute name=“Conventions” type=“string” value=“CF-1.1”/>
    <attribute name=“source” type=“string” value=“Data from model run ABC123”/>
    <variable name=“longitude” shape=“longitude” type=“double”>
        <attribute name=“standard_name” type=“string” value=“longitude”/>
        <attribute name=“units” type=“string” value=“degrees_east”/>
        <attribute name=“bounds” type=“string” value=“bound_longitude”/>
        <attribute name=“axis” type=“string” value=“X”/>
        <values increment=“3.75” npts=“96” start=“0.0”/>
    </variable>
    <variable name=“bound_longitude” shape=“longitude bounds_axis” type=“double”> </variable>
    <variable name=“latitude” shape=“latitude” type=“double”>
        <attribute name=“standard_name” type=“string” value=“latitude”/>
        <attribute name=“units” type=“string” value=“degrees_north”/>
        <attribute name=“bounds” type=“string” value=“bound_latitude”/>
        <attribute name=“axis” type=“string” value=“Y”/>
        <values increment=“-2.5” npts=“73” start=“90.0”/>
    </variable>
    <variable name=“bound_latitude” shape=“latitude bounds_axis” type=“double”> </variable>
    <variable name=“air_pressure” shape=“air_pressure” type=“float”>
        <attribute name=“standard_name” type=“string” value=“air_pressure”/>
        <attribute name=“units” type=“string” value=“hPa”/>
        <attribute name=“axis” type=“string” value=“Z”/>
        <attribute name=“positive” type=“string” value=“down”/>
        <values increment=“70.71429” npts=“15” start=“10.0”/>
    </variable>
    <variable name=“time” shape=“time” type=“double”>
        <attribute name=“calendar” type=“string” value=“360_day”/>
        <attribute name=“standard_name” type=“string” value=“time”/>
        <attribute name=“units” type=“string” value=“days since 2289-1-1”/>
        <attribute name=“bounds” type=“string” value=“bound_time”/>
        <attribute name=“axis” type=“string” value=“T”/>
        <values increment=“360.0” npts=“140” start=“510.0”/>
    </variable>
    <variable name=“bound_time” shape=“time bounds_axis” type=“double”> </variable>
    <variable name=“air_temperature” shape=“time air_pressure latitude longitude” type=“float”>
        <attribute name=“standard_name” type=“string” value=“air_temperature”/>
        <attribute name=“units” type=“string” value=“Kir_temperature”/>
        <attribute name=“long_name” type=“string” value=“temperature on pressure level”/>
        <attribute name=“cell_methods” type=“string” value=“longitude: latitude: mean time: mean (interval: 4 h)”/>
        <attribute name=“_FillValue” type=“float” value=“-1.073742e+09”/>
    </variable>
</netcdf>

B.3.                 GetCoverage response encoding examples

This section details examples of GetCoverage response encodings based on SOAP and Multipart-related technology. -

B.3.1.             SOAP Response returning  an ncML document referring a netCDF binary file included in the message

  MIME-Version:
  1.0
  Content-Type:
  multipart/related;
  boundary="----=_NextPart_000_0000_93251752.3C5526C0"
   
  ------=_NextPart_000_0000_93251752.3C5526C0
  Content-Type:
  application/xml; charset="UTF-8"
   
  <?xml
  version="1.0" encoding="UTF-8"?>
  <soap:Envelope
  xmlns:soap="http://www.w3.org/2001/12/soap-envelope">
    <soap:Header/>
    <soap:Body>
      <Coverages xmlns="http://www.opengis.net/wcs/1.1/ows"
  xmlns:ows="http://www.opengis.net/ows"
  xmlns:xlink="http://www.w3.org/1999/xlink"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:schemaLocation="http://www.opengis.net/wcs/1.1/ows
  ../owsCoverages.xsd http://www.opengis.net/ows
  ../../../ows/1.0.0/ows19115subset.xsd">
        <Coverage>
         
  <ows:Title>Example</ows:Title>
          <ows:Abstract>Example of
  coverage</ows:Abstract>
         
  <Identifier>Example</Identifier>
          <Reference
  href="cid:bfa8e8ac@example.net" />
          <Reference
  href="http://example.net/data/CoverageDataValues.nc" />
          <Reference
  href="http://example.net/data/Dataset.ncml" />
        </Coverage>
      </Coverages>
    </soap:Body>
  </soap:Envelope>
  ------=_NextPart_000_0000_93251752.3C5526C0
  Content-Type:
  application/xml
  Content-ID:
  <bfa8e8ac@example.net>
   
  ...(metadata
  content)...
  ------=_NextPart_000_0000_93251752.3C5526C0
  Content-Type:
  application/CF-netCDF
  Content-Transfer-Encoding:
  base64
  Content-ID: <c3499c27@example.net>
  Content-Location:
  http://example.net/data/CoverageDataValues.nc……
  ...(netCDF
  binary data content, pointed by the ncML dataset)...
  ------=_NextPart_000_0000_93251752.3C5526C0
  Content-Type:
  application/ ncML+xml 
  Content-Transfer-Encoding:
  base64
  Content-ID:
  <1324bc12@example.net>
  Content-Location:
  http://example.net/data/Dataset.ncml
  …..
  ...(
  ncML dataset content)...
  ------=_NextPart_000_0000_93251752.3C5526C0--

B.3.2.             C.3.4 Multipart section containing ncML with binary data included

  ------=_NextPart_000_0000_93251752.3C5526C0
  Content-Type:
  application/CF-netCDF
  Content-Transfer-Encoding:
  base64
  Content-ID:
  <1324bc12@example.net>
  Content-Location:
  http://example.net/data/data2.ncml
   
  <?xml
  version="1.0" encoding="UTF-8"?>
  <netcdf
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     
  xmlns="http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2">
      <dimension name="longitude"
  length="96"/>
      <dimension
  name="bounds_axis" length="2"/>
      <dimension name="latitude"
  length="73"/>
     
  <dimension name="air_pressure" length="15"/>
      <dimension name="time"
  length="140"/>
      <attribute
  name="Conventions" type="string"
  value="CF-1.1"/>
      <attribute name="source"
  type="string" value="Data from model run ABC123"/>
      <variable name="longitude"
  shape="longitude" type="double">
          <attribute
  name="standard_name" type="string"
  value="longitude"/>
          <attribute name="units"
  type="string" value="degrees_east"/>
          <attribute name="bounds"
  type="string" value="bound_longitude"/>
          <attribute name="axis"
  type="string" value="X"/>
          <values increment="3.75"
  npts="96" start="0.0"/>
      </variable>
      <variable
  name="bound_longitude" shape="longitude bounds_axis"
  type="double"> </variable>
      <variable name="latitude"
  shape="latitude" type="double">
          <attribute
  name="standard_name" type="string"
  value="latitude"/>
          <attribute name="units"
  type="string" value="degrees_north"/>
          <attribute name="bounds"
  type="string" value="bound_latitude"/>
          <attribute name="axis"
  type="string" value="Y"/>
          <values increment="-2.5"
  npts="73" start="90.0"/>
      </variable>
      <variable
  name="bound_latitude" shape="latitude bounds_axis"
  type="double"> </variable>
      <variable name="air_pressure"
  shape="air_pressure" type="float">
          <attribute
  name="standard_name" type="string"
  value="air_pressure"/>
          <attribute name="units"
  type="string" value="hPa"/>
          <attribute name="axis"
  type="string" value="Z"/>
          <attribute
  name="positive" type="string" value="down"/>
          <values
  increment="70.71429" npts="15"
  start="10.0"/>
      </variable>
      <variable name="time"
  shape="time" type="double">
          <attribute
  name="calendar" type="string"
  value="360_day"/>
          <attribute
  name="standard_name" type="string"
  value="time"/>
          <attribute name="units"
  type="string" value="days since 2289-1-1"/>
          <attribute name="bounds"
  type="string" value="bound_time"/>
          <attribute name="axis"
  type="string" value="T"/>
          <values
  increment="360.0" npts="140" start="510.0"/>
      </variable>
      <variable name="bound_time"
  shape="time bounds_axis" type="double">
  </variable>
      <variable
  name="air_temperature" shape="time air_pressure latitude
  longitude" type="float">
          <attribute
  name="standard_name" type="string"
  value="air_temperature"/>
          <attribute name="units"
  type="string" value="Kir_temperature"/>
          <attribute
  name="long_name" type="string" value="temperature on
  pressure level"/>
          <attribute
  name="cell_methods" type="string" value="longitude:
  latitude: mean time: mean (interval: 4 h)"/>
          <attribute
  name="_FillValue" type="float"
  value="-1.073742e+09"/>
         
  <values
  xm:xmlmime="binary/octet-stream">Li4uKGJhc2U2NCBlbmNvZGVkIGRhdGEpLi4u...(base64
  encoded data)...BlbmNvZGVkIGRhdGEpLi4u==</values>
      </variable>
  </netcdf>
  ------=_NextPart_000_0000_93251752.3C5526C0--
 

B.3.3.             C.3.5  Multipart section containing ncML with binary data extracted using XOP

  ------=_NextPart_000_0000_93251752.3C5526C0
  MIME-Version:
  1.0
  Content-Type:
  Multipart/Related;boundary=MIME_boundary; 
  type="application/xop+xml";
      start="<12dea45c@example.net
  >";
      startinfo="application/ncML+xml”; 
   
  --MIME_boundary
  Content-Type: application/xop+xml;
  charset=UTF-8; 
     
  type="application/ncML+xml;
  action=\"ProcessData\""
  Content-ID: <12dea45c@example.net>
  Content-Location:
  http://example.net/data/data2.ncml
   
  <?xml version="1.0"
  encoding="UTF-8"?>
  <netcdf
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     
  xmlns="http://www.unidata.ucar.edu/namespaces/netcdf/ncml-2.2">
      <dimension name="longitude"
  length="96"/>
      <dimension
  name="bounds_axis" length="2"/>
      <dimension name="latitude"
  length="73"/>
      <dimension name="air_pressure"
  length="15"/>
      <dimension name="time"
  length="140"/>
      <attribute
  name="Conventions" type="string"
  value="CF-1.1"/>
      <attribute name="source"
  type="string" value="Data from model run ABC123"/>
      <variable name="longitude"
  shape="longitude" type="double">
          <attribute
  name="standard_name" type="string"
  value="longitude"/>
          <attribute name="units"
  type="string" value="degrees_east"/>
          <attribute name="bounds"
  type="string" value="bound_longitude"/>
          <attribute name="axis"
  type="string" value="X"/>
          <values increment="3.75"
  npts="96" start="0.0"/>
      </variable>
      <variable
  name="bound_longitude" shape="longitude bounds_axis"
  type="double"> </variable>
      <variable name="latitude"
  shape="latitude" type="double">
          <attribute
  name="standard_name" type="string"
  value="latitude"/>
          <attribute name="units"
  type="string" value="degrees_north"/>
          <attribute name="bounds"
  type="string" value="bound_latitude"/>
          <attribute name="axis"
  type="string" value="Y"/>
          <values increment="-2.5"
  npts="73" start="90.0"/>
      </variable>
      <variable
  name="bound_latitude" shape="latitude bounds_axis"
  type="double"> </variable>
      <variable
  name="air_pressure" shape="air_pressure"
  type="float">
          <attribute
  name="standard_name" type="string"
  value="air_pressure"/>
          <attribute name="units"
  type="string" value="hPa"/>
          <attribute name="axis"
  type="string" value="Z"/>
          <attribute
  name="positive" type="string" value="down"/>
          <values
  increment="70.71429" npts="15"
  start="10.0"/>
      </variable>
      <variable name="time"
  shape="time" type="double">
          <attribute
  name="calendar" type="string" value="360_day"/>
          <attribute
  name="standard_name" type="string"
  value="time"/>
          <attribute name="units"
  type="string" value="days since 2289-1-1"/>
          <attribute name="bounds"
  type="string" value="bound_time"/>
          <attribute name="axis"
  type="string" value="T"/>
          <values
  increment="360.0" npts="140" start="510.0"/>
      </variable>
      <variable name="bound_time"
  shape="time bounds_axis" type="double">
  </variable>
      <variable
  name="air_temperature" shape="time air_pressure latitude longitude"
  type="float">
          <attribute
  name="standard_name" type="string"
  value="air_temperature"/>
          <attribute name="units"
  type="string" value="Kir_temperature"/>
          <attribute
  name="long_name" type="string" value="temperature on
  pressure level"/>
          <attribute
  name="cell_methods" type="string" value="longitude:
  latitude: mean time: mean (interval: 4 h)"/>
          <attribute
  name="_FillValue" type="float"
  value="-1.073742e+09"/>
          <values
  xm:xmlmime="binary/octet-stream"><xop:Include 
     
  xmlns:xop='http://www.w3.org/2004/08/xop/include' 
     
  href='cid:bd43gh2y@example.net'/>
         
  </values>
     
  </variable>
  </netcdf>
  --MIME_boundary
  Content-Type: application/octet-stream
  Content-Transfer-Encoding: binary
  Content-ID: <bd43gh2y@example.net>
   
  ...(binary
  encoded data)...
  --MIME_boundary--
  ------=_NextPart_000_0000_93251752.3C5526C0--
 

Annex : Revision history

Annex : Bibliography

[1] OGC 11-165r2, CF-netCDF3 Data Model Extension standard, version 3.1, March 2013.

[2] ISO/TC 211, IS 19123:2005 Geographic information — Schema for coverage geometry and functions, ISO/IS 19123:2005

[3] OGC 07-036, OGC® Geography Markup Language (GML) Encoding Standard, version 3.2.1.

[4] OGC 08-094, OGC® SWE Common Data Model Encoding Standard, version 2.0.0.

[5] OGC 10-092, NetCDF Binary Encoding Extension Standard: NetCDF Classic and 64-bit Offset Format, version 1.0.

[6]        S. Nativi, J. Caron, E. Davis and B. Domenico, “Design and implementation of netCDF Markup Language (NcML) and Its GML-based extension (NcML-GML)”, Computers & Geosciences Journal, Volume 31, Issue 9, November 2005, Pages 1104-1118, Elsevier Publication. http://linkinghub.elsevier.com/retrieve/pii/S0098300405001019
http://www.unidata.ucar.edu/software/netcdf/ncml/v2.2/AnnotatedSchema.html

[7]        S Nativi, J Caron, B Domenico, L Bigagli, 2008, Unidata’s common data model mapping to the ISO 19123 data model, Earth Science Informatics, vol.1 n. 2, pp. 59-78

[8]        Domenico, B.; Caron, J.; Davis, E.; Nativi, S.; Bigagli, L., “GALEON: Standards-based Web Services for Interoperability among Earth Sciences Data Systems,” Geoscience and Remote Sensing Symposium, 2006. IGARSS 2006. IEEE International Conference on , vol., no., pp.313,316, July 31 2006-Aug. 4 2006. doi: 10.1109/IGARSS.2006.85

[9]        NASA Community Standard,  ESDS-RFC-004: The Data Access Protocol – DAP 2.0 available at: http://www.esdswg.org/spg/rfc/ese-rfc-004

[10]      NASA ESDS–RFC-021 Technical Working Group Final Report.

[11]      NASA ESDS-RFC-021v0.02, CF Metadata Conventions, April 2010.

[12]      IETF RFC 2045,         Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies

[13]      IETF RFC 2046,         Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types

[14]      OGC 06-121r9, OGC Web Services Common Standard

[15]      IETF RFC 2387, The MIME Multipart/Related Content-type

[16]      W3C, SOAP Message Transmission Optimization Mechanism

[17]      W3C, XML-binary Optimized Packaging

[1] Future extension to ISO 19111 (see ISO/CD19111-2) may permit parametric CRS, that would accommodate the pressure axis.