Global Positioning System Reference
In-Depth Information
In a WFS the use of three normative namespaces is also defi ned, namely:
http://www.opengeospatial.net/wfs for the WFS interface
vocabulary.
http://www.opengeospatial.net/gml for the GML vocabulary.
http://www.opengeospatial.net/ogc for the OGC Filter vocabulary.
Finally, as for the underlying transport protocol, at least one between
the HTTP GET and the HTTP POST methods has to be supported and
response messages should be accompanied by the appropriate MIME type
and by other appropriate HTTP entity headers. Moreover, with the HTTP
POST method, the usage of SOAP is also possible. In fact, a client may
send requests by using a SOAP message and the WFS may respond with
another SOAP message. Nothing is mentioned about the structure of the
SOAP Header.
Web Coverage Services
The Web Coverage Service (WCS) standard defi nes an interface for the
exchange of geospatial information representing phenomena known as
coverages that can vary in space and time, a specialized class of features
(Baumann 2010). Like WMS and WFS, in WCS a client has the possibility
to specify the desired criteria for its queries. The mandatory operations
that a WCS service has to support are: GetCapabilities, DescribeCoverage
(a client submits a list of coverage identifi ers and the service returns, for
each identifi er, the description of such coverage) and GetCoverage (a client
requests the processing of a particular coverage from a WCS service).
The use of the HTTP GET with KVP encoding or HTTP POST with XML
encoding are both supported in WCS. In addition, the “OGC WCS XML/
SOAP Protocol Binding Extension document” specifi es how WCS clients
and servers can communicate using the SOAP protocol.
Services Composition
One of the primary properties that should be guaranteed when realizing
services consists in their seamless integration. Indeed, in addition to being
platform or operating system independent, one of the hallmarks of service
philosophy is the possibility to compose two or more services, developed by
different entities, in order to obtain a higher-level service that can meet needs
of a company or an institution. However, despite the simplicity behind the
general idea of services composition and some basic assumptions, such as
the subdivision of the involved services into the three general categories, and
the use of XML for messages exchanges, services composition is a complex
task and several facets must be wisely considered. As clearly explained in
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