Hi all,

Consider the following extract of an App-Schema defined feature type:

   (...)
   <st:Station gml:id="st.1">
   <st:name>station1</st:name>
   <st:position>
   *<st:location>**
   **        <gml:Point srsDimension="2" 
srsName="http://www.opengis.net/gml/srs/epsg.xml#4326";>**
   **            <gml:pos>-1.0 1.0</gml:pos>**
   **        </gml:Point>**
   **    </st:location>*
   <st:name>Europe</st:name>
   </st:position>
   <st:measurements>
   <ms:Measurement gml:id="ms.1">
   <ms:name>temperature</ms:name>
   </ms:Measurement>
   </st:measurements>
   (...)

Since the geometry is in a sub element it will not be recognized as the default 
geometry and we need
to specify in the SLD the geometry XPath. My first try was to use the following 
XPath:

   <ogc:PropertyName>*st:Station**/*st:position/st:location</ogc:PropertyName>

To my surprise this didn't work, after debugging the code it looks like the root feature type should not
be provided at the start of the XPath, so this is what should be used:

   <ogc:PropertyName>*st:position/st:location*</ogc:PropertyName>

Consider the following valid SLD, note the filter usage:

   <?xml version="1.0" encoding="UTF-8"?>
   <StyledLayerDescriptor version="1.0.0"
   xmlns="http://www.opengis.net/sld";
   xmlns:gml="http://www.opengis.net/gml/3.2";
   xmlns:ms="http://www.measurements.org/1.0";
   xmlns:ogc="http://www.opengis.net/ogc";
   xmlns:sld="http://www.opengis.net/sld";
   xmlns:st="http://www.stations.org/1.0";
   xmlns:xlink="http://www.w3.org/1999/xlink";
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";
   xsi:schemaLocation="http://www.opengis.net/sld StyledLayerDescriptor.xsd">
   <NamedLayer>
   <Name>stations</Name>
   <UserStyle>
   <FeatureTypeStyle>
   <Rule>
   <Name>stations</Name>
   <ogc:Filter>
   <PropertyIsEqualTo>
   <PropertyName>*st:measurements/ms:Measurement/ms:name*</PropertyName>
   <Literal>wind</Literal>
   </PropertyIsEqualTo>
   </ogc:Filter>
   <PointSymbolizer>
   <sld:Geometry>
   <ogc:PropertyName>*st:position/st:location*</ogc:PropertyName>
   </sld:Geometry>
   <Graphic>
   <Mark>
   <WellKnownName>square</WellKnownName>
   <Fill>
   <CssParameter name="fill">#FF0000</CssParameter>
   </Fill>
   </Mark>
   <Size>6</Size>
   </Graphic>
   </PointSymbolizer>
   </Rule>
   </FeatureTypeStyle>
   </UserStyle>
   </NamedLayer>
   </StyledLayerDescriptor>

The same filter in a WFS GetFeature request will needs to be encoded like this:

<wfs:GetFeature outputFormat="gml3" service="WFS" version="1.1.0"
    xmlns:ms="http://www.measurements.org/1.0";
    xmlns:ogc="http://www.opengis.net/ogc";
    xmlns:st="http://www.stations.org/1.0";
    xmlns:topp="http://www.openplans.org/topp";
    xmlns:wfs="http://www.opengis.net/wfs";
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";
    xsi:schemaLocation="http://www.opengis.net/wfs 
http://schemas.opengis.net/wfs/1.1.0/WFS-basic.xsd";>
    <wfs:Query typeName="st:Station">
        <ogc:Filter>
            <ogc:PropertyIsEqualTo>
                <ogc:PropertyName>
*st:Station/st:measurements/ms:Measurement/ms:name*
                </ogc:PropertyName>
                <ogc:Literal>wind</ogc:Literal>
            </ogc:PropertyIsEqualTo>
        </ogc:Filter>
    </wfs:Query>
</wfs:GetFeature>

In this case the root feature type name needs to be provided at the beginning 
of the XPath.

Conclusion, the way of referencing properties of App-Schema defined feature 
types is different
in WFS and WMS (at least for GetFeatrue and SLDs).

In my opinion the WFS GetFeature full XPath path is the most natural one and 
both WFS and
WMS should use \ accept the same XPath.

I propose to allow the use of the full XPath in WMS (equal to WFS) but keep 
accepting the shorten
one in WMS for compatibility reasons, opinions ?

My plan is to store as user data the target root name and root type name here:
https://github.com/nmco/geotools/blob/22ab45c198130388c7774d8d43b051fc7a7402e6/modules/extension/app-schema/app-schema/src/main/java/org/geotools/data/complex/config/AppSchemaDataAccessConfigurator.java#L297

and then in the feature accessor remove the root element from the XPath id needed (based on the user data):
https://github.com/nmco/geotools/blob/66a9c89239d7a7ae6526399b57eb28649b5620c2/modules/extension/complex/src/main/java/org/geotools/filter/expression/FeaturePropertyAccessorFactory.java#L257-L285

This is the best way I found to do it ... better idea ?

Cheers,

Nuno Oliveira

--
Regards,
Nuno Oliveira
==
GeoServer Professional Services from the experts! Visit http://goo.gl/it488V 
for more information.
==

Nuno Miguel Carvalho Oliveira
@nmcoliveira
Software Engineer

GeoSolutions S.A.S.
Via di Montramito 3/A
55054  Massarosa (LU)
Italy
phone: +39 0584 962313
fax:      +39 0584 1660272

http://www.geo-solutions.it
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