[OpenSDI] associating WFS or WCS to WMS services - how-to?

[Josh at oklieb]

Jeroen,

You could certainly put a WFS / WCS URL in to DataURL, but that does  
not have a place for describing the semantic of the URL except as an  
opaque reference. Fine for a client with inside knowledge, but not  
very general.

Most combined services provide an implicit link by naming the layer  
and the featuretype identically. This is also not very general or  
explicit.

My suggestion for now as a more general approach would be to use the  
same MetadataURL for all service offerings (layers, featuretypes,  
coverages, etc.) based on the same data. There can also be multiple  
MetadataURL's in an offering, distinguished by a language or schema  
label. One could even define a dataIdentifier schema (e.g. URN  
schema) to hold this specific ID information. Yes, at least one  
MetadataURL  should point at a real data description, but a URI it  
can also be a global key for the association across any number of  
services. A client could then match the URI between capabilities  
documents to determine the association and a catalog could show (all  
of) the service offerings for a given dataset.

Cheers,

Josh

On Nov 9, 2005, at 1:19 PM, Jeroen Ticheler wrote:

> Hi!
> We are trying to find the (most suitable) way of associating a WFS  
> or a WCS to an existing WMS service. The purpose of this is that we  
> can use WMS to display the interactive maps while we use the WFS/ 
> WCS to extract data from the server and make it available to the  
> user as GML, shapefile, GeoTIFF etc... to be downloaded from an FTP  
> or directly for local use.
>
> The problems we have are two-fold:
> 1- What is the best location in a Capabilities document to do this?  
> We want our client application to know of the existence of the WFS  
> or WCS service.
>   What we think as best candidates are:
>
>   - the DataURL element
>
> (definition: A server may use DataURL to offer a link to the  
> underlying data represented by a particular layer. The
> enclosed Format element indicates the file format MIME type of the  
> data file.)
>
>        - or the FeatureListURL element
>
> (definition: A server may use a <FeatureListURL> element to point  
> to a list of the features represented in a Layer.
> FeatureListURL is not inherited by child layers. The enclosed  
> Format element indicates the file format MIME
> type of the feature list.)
>
> 2- If we use one of these, we think of putting in the link to the  
> service and a suitable MIME type. We have seen the following MIME  
> types used for WMS and WFS getCapabilities requests, but are not  
> sure they are standard and also we didn't find any reference to a  
> similar WCS MIME type. What to do???
>
> We found:
>
>        application/vnd.ogc.wms_xml
>
> and
>
>         application/vnd.ogc.wfs_xml
>
>         - Should we use these MIME types to indicate the URL points  
> to a WMS or WFS getCapabilities?
>        - Should we assume we can use    application/ 
> vnd.ogc.wcs_xml        for a WCS getCapabilities MIME type!?
>
> We have not found any of the application/vnd.ogc MIME type  
> registered at http://www.iana.org/assignments/media-types/  What  
> should be our conclusion on that?
>
> Thanks in advance!
> Ciao,
> Jeroen & Stefano
>
>
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