[mapserver-dev] RFC 118 - Vendor-specific WMS FILTER parameter

[Rahkonen Jukka (MML)]

Hi,

I doubt anybody is using the FILTER vendor option with Geoserver because it supports CQL_FILTER  which is much less painless to use 
http://docs.geoserver.org/latest/en/user/filter/ecql_reference.html#filter-ecql-reference
http://docs.geoserver.org/latest/en/user/tutorials/cql/cql_tutorial.html#cql-tutorial

I guess that OGC XML filter is easier to implement for us. It seems by the RFC that these filters could be simplified when it comes to namespaces which makes them shorter and easier to write even the same filter would not work with schema validating servers:

Mapserver filter:
<Filter><DWithin><PropertyName>Geometry</PropertyName><gml:Point><gml:coordinates>-60.18,46.10</gml:coordinates></gml:Point><Distance units='dd'>0.05</Distance></DWithin></Filter>

Geoserver filter:
filter=%3CFilter%20xmlns:gml=%22http://www.opengis.net/gml%22%3E%3CIntersects%3E%3CPropertyName%3Ethe_geom%3C/PropertyName%3E%3Cgml:Point%20srsName=%224326%22%3E%3Cgml:coordinates%3E-74.817265,40.5296504%3C/gml:coordinates%3E%3C/gml:Point%3E%3C/Intersects%3E%3C/Filter%3E

This reminds me about one practical problem with using OGC filters for spatial queries: User should know the name of the geometry field. If WFS is not active then Mapserver users do not have any way to know what name to use because we do not support DescribeLayer, or do we?
However, Mapserver does internally know what geometry to use and also WFS BBOX query works as KVP without giving the name of the geometry column.

Suggestion: do not require PropertyName in spatial filters, or accept anything 
<PropertyName>Foo</PropertyName>

The example is GML2, would filter be limited to that or should it support also GML3? That would bring troubles, not least with srsName and axis order. How about srsName and default projection? If srsName is not given with the geometry in filter, is it interpreted to be the same as the SRS/CRS of GetMap?

-Jukka Rahkonen-




________________________________________
Daniel Morissette wrote:
[mapserver-dev] RFC 118 - Vendor-specific WMS FILTER parameter

Hi Devs,

FYI I just added RFC 118 about the addition of a vendor-specific FILTER
parameter in the WMS interface to allow easier filtering of GetMap and
GetFeatureInfo requests by client-side JS applications:

http://mapserver.org/development/rfc/ms-rfc-118.html

I will leave the RFC open for discussions for the next few days and will
be working on this during the code sprint this week.

Daniel
--
Daniel Morissette
http://www.mapgears.com/
T: +1 418-696-5056 #201

http://evouala.com/ - Location Intelligence Made Easy
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