[mapserver-dev] WCS 2.0 support and specification compliance

[Andrea Aime]

Hi all,
sorry to intrude on the MapServer dev mailing list, but I'd have a question
that
only the people that implemented the WCS 2.0 support could answer.

I see that the MapServer autotest has requests that comprise parameters
which
are not part of the official specification, which add support for scaling
and reprojection.
For example:

<?xml version="1.0" encoding="UTF-8"?><wcs:GetCoverage xmlns:wcs="
http://www.opengis.net/wcs/2.0" service="WCS"
version="2.0.0"><wcs:Format>image/tiff</wcs:Format><wcs:CoverageID>grey</wcs:CoverageID><wcs:DimensionTrim><wcs:Dimension
crs="http://www.opengis.net/def/crs/EPSG/0/4326">lon</wcs:Dimension><wcs:TrimLow>-121.488</wcs:TrimLow><wcs:TrimHigh>-121.487</wcs:TrimHigh></wcs:DimensionTrim><wcs:DimensionTrim><wcs:Dimension
crs="http://www.opengis.net/def/crs/EPSG/0/4326
">lat</wcs:Dimension><wcs:TrimLow>0.000</wcs:TrimLow><wcs:TrimHigh>0.001</wcs:TrimHigh></wcs:DimensionTrim></wcs:GetCoverage>

(the Dimension element does not have a crs attribute in the official spec).

<?xml version="1.0" encoding="UTF-8"?><wcs:GetCoverage xmlns:wcs="
http://www.opengis.net/wcs/2.0" service="WCS"
version="2.0.0"><wcs:Format>image/tiff</wcs:Format><wcs:CoverageID>grey</wcs:CoverageID><wcs:Size
dimension="x">10</wcs:Size><wcs:Size
dimension="y">20</wcs:Size></wcs:GetCoverage>
or
<?xml version="1.0" encoding="UTF-8"?><wcs:GetCoverage xmlns:wcs="
http://www.opengis.net/wcs/2.0" service="WCS"
version="2.0.0"><wcs:Format>image/tiff</wcs:Format><wcs:CoverageID>grey</wcs:CoverageID><wcs:Resolution
dimension="x">20</wcs:Resolution><wcs:Resolution
dimension="y">20</wcs:Resolution></wcs:GetCoverage>

(there is no Size and Resolution element in the specification)

The WCS 2.0 specification says that the scaling, interpolation, band
subsettting and reprojection should have been
addressed by application profiles that, to date, have not been released,
but my understanding is that in POST
requests these extra things would have to be added inside the wcs:Extension
element.

I also see there is a KVP syntax for them in MapServer.

Long story short, I'm wondering, where is the above coming from? Is it
educated guesses from the MapServer
developers, or coming from documents that OGC never released (or that yours
truly simply did not find?).
I also looked in other software (Rasdaman) and there is apparently no trace
of handling these extra parameters

Cheers
Andrea
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