KVP Options example XML Options example
Copyright © 2012 Open Geospatial Consortium
45 The way in which to specify this parameter in a KVP request would be to use the period .
between the parameter name and its parents. A fully qualified parameter name shall identify the parameter completely. Its value will follow the equal sign.
For example, consider the Format parameter for Video Service. The server may choose to set possible values to this parameter as the IETF approved MIME types of videompeg,
videoquicktime, and videox-msvideo.
Let us pick the Format=videompeg. Within this format, let us say, the server supports MISB compliant MPEG2 transport streams. Within this transport stream, let us say, it supports H.264
and MPEG2 encoding. For H.264 and MPEG2, it supports bit rate, GOP size, playback frame rate, and Chroma sub-sampling. How can we have a list of parameters that allow for the client to
set these values without making it a part of the specification? Example features:
Format=videompeg Video.Mpeg=Mpeg2
Video.Mpeg.Mpeg2.Codec=H264 Video.Mpeg.Mpeg2.Codec.H264.BitRate=2500
Video.Mpeg.Mpeg2.Codec.H264.GOP=10 Video.Mpeg.Mpeg2.Codec.H264.FrameRate=29.97
Video.Mpeg.Mpeg2.Codec.H264.ChromaSubSampling=422
We can do this in one of two ways. Both ways require the Capabilities response to send back the syntax of each parameter as a parameter tree. The “.”character should be used to traverse the
hierarchy to make a fully qualified unique parameter name. Values have data types, ranges, defaults and constraints; however they are not defined as part of the specification. They are
defined as part of the Capabilities response from the service implementation and follow a specification.
Note that [OGS WSCS] section 11.5.5 specifically limits parameters to a deterministic finite set. However, this is to satisfy the goal of constructing a WSDL file with input request parameters.
The WAMI spec defines BOTH a KVP parameter space and an XML request document parameter space. Any WSDL resource will leverage the XML parameter space, wherein only a
single Options element contains the entire hierarchy of options.