TJS DescribeDatasets Operation

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TJS DescribeDatasets Operation


The DescribeDatasets operation returns an XML document that identifies all of the attribute datasets for which data is available from the service instance. There may be one or more attribute datasets that apply to any spatial framework. The response includes descriptive information about each dataset available from the service instance, and information that uniquely identifies each dataset. This description can be used to automatically build a user interface to identify the dataset from which the user would like to obtain attribute data.


DescribeDatasets Request

Parameters

Name Presence Description
service Required Identifies service type. Must be "TJS".
request Required Identifies service request. Must be "DescribeDatasets".
version Required Identifies service version. Defaults to the latest available version, currently 1.0.
language Optional Determines the language of the human-readable content of the response. Value is a two or five character IETF RFC 4646 language identifier.
FrameworkURI Optional The URI of the framework dataset, as indicated in the DescribeFrameworks response.
DatasetURI Optional The URI of an attribute table which can be joined to the spatial framework identified by the FrameworkURI. DatasetURIs are normally unknown during an initial DescribeDatasets request to the server, and therefore this parameter is normally absent from such a request. If this parameter is absent, the response shall include descriptions for all datasets available for the specified framework(s).

Methods

HTTP GET method using KVP (mandatory)

All TJS servers shall implement HTTP GET transfer of the DescribeDatasets request, using KVP encoding. The KVP encoding of the DescribeDatasets request shall use the parameters specified above. An example of a DescribeDatasets request via HTTP GET is:

http://foo.bar/foo?
   service=TJS&
   request=DescribeDatasets&
   version=1.0&
   language=en&
   FrameworkURI=http://nrcan.gc.ca/Provinces/2001

Note: URL encoding of KVP values in this example has been removed for clarity.


HTTP POST method using XML (optional)

TJS servers may also implement HTTP POST transfer of the DescribeDatasets operation request, using XML encoding only. The request parameters are encoded as XML elements, with their contents identical to those indicated in the parameter table shown above according to the DescribeDatasets request XML schema. The following example indicates the contents and structure of a DescribeDatasets operation request encoded in XML.

<DescribeDatasets service="TJS" version="1.0" language="en">
  <FrameworkURI>http://nrcan.gc.ca/Provinces/2001</FrameworkURI>
</DescribeDatasets>



DescribeDatasets Response

Schema

The normal response to a valid DescribeDatasets operation request shall be a DatasetDescriptions data structure, which contains descriptions of one or more Datasets for which data is available on this service. This document is encoded in XML according to the DescribeDatasets response XML schema.

Examples


Exceptions

When a TJS server encounters an error while performing a DescribeDatasets operation, it shall return an exception report message as specified in Clause 8 of [OGC 06-121r3]. The allowed exception codes shall include those listed in Table 5 of Subclause 7.4.1 of [OGC 06-121r3].


For more information on structuring requests, please see the TJS Standard.