[Users] DescribeLayer and DescribeFeatureType

[Matt Priour]

I think these requests have merit and make automatic configuration of the 
underlying feature store easier.
However:
How would we know if WFS was available and its URL?
ESRI ArcGIS Server & ArcIMS both have different URLs for WMS & WFS, which 
depending on how the admin has configured it may or may not be decipherable 
from the WMS url.
Also, many servers don't have WFS turned on.

Are these things that the LayerStore would guess at or would they be 
required configuration options for this functionality to be accessible?

Matt Priour
Kestrel Computer Consulting
www.kestrelcomputer.com
--------------------------------------------------
From: "Bart van den Eijnden (OSGIS)" <bartvde at osgis.nl>
Sent: Tuesday, February 17, 2009 12:37 PM
To: <users at geoext.org>
Subject: [Users] DescribeLayer and DescribeFeatureType

> Hi list,
>
> today Andreas and I had an interesting discussion about WMS
> DescribeLayer and WFS DescribeFeatureType.
>
> Let me first give a bit of background for people not familiar with these
> requests.
>
> WMS DescribeLayer is currently part of the SLD WMS spec, and is meant to
> tie a WMS layer to a WFS typename or WCS coverage. Not all WMS services
> implement this though, Mapserver and Geoserver do, but e.g. ArcGIS
> Server currently does not. There are plans to move the DescribeLayer
> request from SLD WMS to mainstream WMS in WMS 1.4. A simple parser for
> WMS DescribeLayer response is in [1].
>
> Currently a lot of applications by-pass WMS DescribeLayer and assume WMS
> OnlineResource = WFS OnlineResource and WMS layer name = WFS typename.
> Although this will work in some cases, it will fail in others, but it
> saves a trip to the server. So a question for GeoExt is: do we want to
> follow the OGC way in this? I would be in favour of using WMS
> DescribeLayer even if this is an extra round-trip to the server. But
> what do others think?
>
> WFS DescribeFeatureType is a way to get an XML Schema back describing
> the structure of a typename, to put it more simple it will return a list
> of attributes from a layer. This can be used then to e.g. fill combo
> boxes for layer attributes, for a querybuilder component for instance.
> Btw a WFS DescribeFeatureType parser was just committed to OpenLayers
> trunk this weekend by Andreas [2].
>
> The solution to integrate this into GeoExt that Andreas just came up
> with is everytime a WMS layer is added to the LayerStore, we will
> perform a DescribeLayer and subsequently a WFS DescribeFeatureType
> request and store this information in the LayerStore.
>
> Does this approach make sense? Thoughts?
>
> Best regards,
> Bart & Andreas
>
> [1] http://trac.openlayers.org/ticket/1201
> [2] http://trac.openlayers.org/ticket/1202
>
> -- 
> Bart van den Eijnden
> OSGIS, Open Source GIS
> bartvde at osgis.nl
> http://www.osgis.nl
>
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