[OSGeo-Discuss] displaying complex GML in web-based enviroment (with deegree)

[Markus Schneider]

Hello list,

I would like to add some information to the prior discussion regarding deegree's capabilities for visualizing (and
generally deploying) complex GML application schemas.

GML and application schema support / data model
-----------------------------------------------

This determines the supported GML version and the level of complex GML application schema support (e.g. in the WFS, but
also relevant for the data backends used for WMS). This needs to be differentiated between deegree 2 and 3 (upcoming,
only available via SVN at the moment [1]):

deegree 2:

- GML 3.1.1
- GML 2.1.2 (via XSL)
- GML 3.2.1 (via XSL)
- Generally supports complex GML schemas (nested features), but is a bit limited (e.g. doesn't support element
definitions that use the ref-attribute or GML measure types). However this can be alleviated by plugging in XSL-scripts.

deegree 3

- GML 2.1.2, 3.0.2, 3.1.1 and GML 3.2.1 supported natively
- Aims for full GML application schema support. Already tested and working: GeoSciML, XPlanung 2 + 3, INSPIRE Annex I
schemas (Addresses)

Although deegree 3 still requires some work concerning the backend side (i.e. relational mapping), there are already two
demo installations that demonstrate the support for complex GML application schemas in the WFS:

- INSPIRE Annex I: http://inspire.kademo.nl/deegree-inspire-demo -> "Click Client"
- XPlanung 2 / 3: http://lkee-xplanung2.lat-lon.de/xplan-wfs/client/client.html

Visualization
-------------

For visualizing of complex features, I see two options:

1. Using a WMS (based on styling complex features)
2. Using a WFS client that renders the complex features itself

deegree 2:

- WMS: No support for styling complex features
- WFS client: iGeoDesktop (deegree2-based) has some support for visualizing complex features, but this is limited to the
data model of deegree 2 and not tested very well

deegree 3:

- WFS client: No deegree 3-based WFS client is available yet
- WMS: Complex features can be styled directly. In that case, the SLD/SE code can use XPath-expressions to reference
nested properties. Here's an example for the visualization of INSPIRE Address features (note the PropertyName element):

...
    <PointSymbolizer>
      <Geometry>
        <ogc:PropertyName>ad:position/AD:GeographicPosition/AD:geometry</ogc:PropertyName>
      </Geometry>
      <Graphic>
        <Mark>
          <WellKnownName>circle</WellKnownName>
          <Fill>
            <CssParameter name="fill">#111111</CssParameter>
            <CssParameter name="fill-opacity">1.0</CssParameter>
          </Fill>
        </Mark>
        <Size>11</Size>
      </Graphic>
    </PointSymbolizer>
...

This style is also used in the demonstration here: http://inspire.kademo.nl/deegree-inspire-demo -> Click Map

If you're interested in checking out deegree 3 for deploying/visualizing complex application schemas, there are
currently the following options:

- Inspire FOSS project (by Just van de Broecke) contains the code for the deegree-inspire-demo linked above
- Check out deegree 3 from SVN [1] and contact mailing lists [2] for info (the documentation is sparse right now)

Best regards,
Markus

[1] http://wiki.deegree.org/deegreeWiki/deegree3/BuildingDeegree3
[2] http://wiki.deegree.org/deegreeWiki/GettingInvolved#MailingLists

-- 
Markus Schneider

l a t / l o n  GmbH
Aennchenstrasse 19           53177 Bonn, Germany
phone ++49 +228 184960       fax ++49 +228 1849629
http://www.lat-lon.de        http://www.deegree.org

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