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". |
| Version | Required | Identifies service version. Defaults to the latest available version, currently 1.0. |
| Request | Required | Identifies service request. Must be "DescribeDatasets". |
| AcceptLanguages | Optional | Determines the language of the human-readable content of the response. Consists of a list of RFC 4646 language tags, comma-delimited and in order of preference. |
| FrameworkURI | Optional | The URI of the framework dataset, as indicated in the DescribeFrameworks response. |
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&
Version=1.0&
Request=DescribeDatasets&
AcceptLanguages=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" acceptLanguages="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.