[auscope-geosciml] WFS query with xlink:href [SEC=UNCLASSIFIED]
alistair.bh.ritchie at gmail.com
Sun May 15 19:22:19 EDT 2011
If you mean querying property values on the target of an xlink? Yes it can,
provided it is properly configured (obviously).
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On 16 May 2011 09:13, <Oliver.Raymond at ga.gov.au> wrote:
> >> ACTION Marcus to check if Snowflake will allow us to query attribute
> >> values in Xpath including xlink:href. (Result: tested during meeting
> >> and it does.) ACTION CP to check if XtraServer will (tested after
> >> meeting and it does).
> A question for the Geoserver gurus. Does Geoserver have any problems with
> performing queries on attribute values in xlink:hrefs?
> -----Original Message-----
> From: Sen, Marcus A. [mailto:mase at bgs.ac.uk]
> Sent: Wednesday, 11 May 2011 7:10 PM
> To: Raymond Oliver; Bruce.Simons at dpi.vic.gov.au
> Cc: eboisver at nrcan.gc.ca; Guillaume.Duclaux at csiro.au; Simon.Cox at csiro.au;
> steve.richard at azgs.az.gov; portele at interactive-instruments.de; Duffy, Tim
> Subject: RE: Testbed 4 - Geochemistry
> > -----Original Message-----
> > From: Oliver.Raymond at ga.gov.au [mailto:Oliver.Raymond at ga.gov.au]
> > Sent: 11 May 2011 03:23
> > I don't see a requirement for a GeologicSamplingMethod WFS.
> > GeologicSamplingMethod is really just a pointer to a vocabulary, and we
> > are adopting a best practice of using xlink:href and xlink:title to
> > deliver vocabulary terms in GeoSciML.
> We have a bit of an outstanding issue with our use of xlink:href's for
> remote property values. When we had a meeting with Clemens Portele in
> Edinburgh earlier this year he expressed a concern about some of our use of
> xlink:href where we just use the values of the URI or we are going to point
> to a vocab in RDF/SKOS. This is a bit of a mismatch with the GML feature
> model. We might keep some kind of GML serialization as an alternative to
> possibly be at the end of these href's as well as RDF/SKOS (or nothing where
> we just use the URI as an identifying value) so that Filter Encoding Spec
> queries can be done on their properties. Or we could define some new rules
> for how we handle encoding and querying non-GML property values in a GML
> Application Schema for putting to OGC. I guess we have implicitly settled on
> a best practice for our own use but should we document this explicitly for
> submitting some kind of recommendation to OGC?
> I quote the relevant parts of our meeting notes below that Tim circulated
> to the auscope list on 7th March this year.
> How to query by reference properties especially controlled vocab properties
> which we are now specifying with xlink:href URIs given that strictly we
> can't necessarily query on XML attribute values (they aren't properties in
> the GML feature model) and that their serialisation (if any) may be
> variable. E.g. RDF/XML won't nescessarily have a consistent XML encoding for
> same RDF model so an Xpath query isn't appropriate. Perhaps we need some
> kind of OGC change request for querying on identifiers which are URIs.
> (Also, general question of combining linked data triple type queries with
> GML feature model Xpath type queries.) ACTION probably up to wider community
> to work out querying XML and RDF data together.
> We do need some mechanism for our queries on the identifiers of dictionary
> terms (mostly) that are URIs in the values of xlink:href attributes. This
> can be made to work by allowing attribute specifiers to appear in your query
> Xpaths but this is strictly outside the subset of Xpath that is required by
> WFS/FES and also is really abusing the intended role of xlink:href in GML
> which is really for pointing at a further serialisation and could be
> resolved by a WFS2 value-of() function so that the contents could be
> queried. In a pure GML implementation the identifier query would use a path
> name like .../value-of(gsml:geologicUnitType)/gml:identifier but we are now
> serialising our dictionaries in SKOS/RDF not GML. This is difficult in any
> case as it would require remote resolving capability, which is problematic
> in general for performance reasons and typically not supported be WFS
> implementations. CP will think about. Maybe we could add GML representations
> as well as SKOS that could
> be retrieved from the HTTP-URIs. ACTION Marcus to check if Snowflake will
> allow us to query attribute values in Xpath including xlink:href. (Result:
> tested during meeting and it does.) ACTION CP to check if XtraServer will
> (tested after meeting and it does).
> Shouldn't this discussion be on the auscope list?
> I've added Clemens to the CC list but when I used this address a yesterday
> I got an undeliverable response. Does anyone know if his email has changed
> or was this just a temporary problem?
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