[esip-semanticweb] help with marking up WMS/WCS Capability docs?
Christopher Lynnes
Chris.Lynnes at nasa.gov
Thu Jul 16 17:20:02 EDT 2009
On Jul 16, 2009, at 5:08 PM, Benno Blumenthal wrote:
>
>
> On Thu, Jul 16, 2009 at 4:56 PM, Christopher Lynnes <Chris.Lynnes at nasa.gov
> > wrote:
> So you are saying it would be something like:
>
> <Keyword
> xmlns:xlink="http://www.w3.org/1999/xlink"
> xmlns:role="http://someuri_root/dataset">
> OMI_A_G
> </Keyword>
>
> No, that is not what I meant. Ignore for the moment that I have
> not reviewed WMS Schema so that this is not legal there, i.e. still
> need to find the proper place for this
>
> What I meant was that is is either an object, i.e.
>
> <Keyword
> xmlns:xlink="http://www.w3.org/1999/xlink"
> xlink:role="http://someuri_root#dataset"
> xlink:href="http://somecontrolled_vocabulary_uri_root#OMI_A_G" />
OK, then this would actually be:
<Keyword
xmlns:xlink="http://www.w3.org/1999/xlink"
xlink:role="http://somecontrolled_vocabulary_uri_root#dataset"
xlink:href="http://somecontrolled_vocabulary_uri_root#OMI_A_G" />
...in that "dataset" is also controlled, representing a class, whereas
OMI_A_G is an instance of the class.
I can see how that would work, but it may be counterintuitive to the
"users", i.e., the data providers who will mark up the Capabilities
documents. This is because their original idea was to reuse the
<Keyword> element, yet they are putting no contents in it!
The machine tag alternative, while less rigorous, may be more
intuitive to them, e.g.:
<Keyword>esip:dataset=OMI_A_G</Keyword>
("esip" is used as a notional namespace in this case.) This may be
good enough for their use case in that it is more important to control
the attribute (i.e., class) side of the equation than the value (i.e.,
instance) side.
>
> where we are representing the controlled vocab as an URI, or
>
> <Metadata xmlns:myns="http://someuri_root#">
> <myns:dataset>OMI_A_G</myns:dataset>
> </Metadata>
>
> where myns:dataset implies a restricted set of possible strings as
> values, i.e. a controlled vocabulary.
>
> Benno
>
>
>
> On Jul 16, 2009, at 4:40 PM, John Graybeal wrote:
>
> To the best of my knowledge, the use of role and arcrole[2] within
> xlink[1] to specify the purpose of the locator (href) attribute is
> limited only to requiring URIs. So you can create a vocabulary that
> describes any set of roles that you want.
>
> John
>
> [1] xlink semantics: http://www.w3.org/TR/xlink/#att-method
> [2] Role, Arcrole, and Title: http://www.w3.org/TR/xlink/#link-semantics
>
> On Jul 16, 2009, at 1:15 PM, Benno Blumenthal wrote:
>
> Hello Chris,
>
> I have not chimed in yet because I have not had a chance to review
> the options for metadata in WMS, and I wanted to say something
> precise. Essentially if you just want controlled vocabulary, XML
> and RDF are quite similar (i.e. if Brian's machine tag implies a
> particular controlled vocabulary for the value, then you have
> represented the information isomorphically to using RDF objects for
> the concepts, and you can crosswalk). If you want to relate two
> objects, the xlink is XML's version of what is native in RDF, but I
> think xlink is very limited as to the meanings of the connections,
> whereas RDF lets the connection's meaning be specified explicitly
> according to a convention.
>
> But meanwhile, could you explain your example more fully -- I don't
> understand what
>
> dataset=OMI_A_G
>
> means (you called it a relationship).
>
> Benno
>
> On Thu, Jul 16, 2009 at 3:55 PM, Christopher Lynnes <Chris.Lynnes at nasa.gov
> wrote:
> On Jul 15, 2009, at 6:52 PM, John Graybeal wrote:
>
> I am not deep in any one of these details, but I am a little familiar
> with all the possibilities you mention. So consider the following as
> notions to be verified:
>
> 1) RDFa won't fit gracefully into the OGC schema as written, because
> it is using a different set of elements (that is, it is tuned to the
> HTML elements). "To date, because XHTML is extensible while HTML is
> not, RDFa has only been specified for XHTML 1.1." [1] The way it
> works is to add attributes, which must be in an RDFa-compatible XHTML
> schema if the document is to validate.
>
> 2) I wholeheartedly endorse the intent to use controlled vocabularies
> in a way that is compatible with the semantic web. All that should be
> necessary to do this is to find a suitable place where a URI can be
> placed. Then you can create controlled vocabularies whose terms
> correspond to URIs. There is extensive guidance on this topic at the
> MMI site [2]. I do not know of any reason these approaches would be
> incompatible with the ESIP ontologies.
>
> 3) The way OOSTethys [1] chose to add more specific descriptions/
> references to SensorML/O&M was through the use of xlink, which is
> supported in the OGC schema. Examples are on the OOSTethys site. As
> far as I know, this is the most used OGC practice to meet this need to
> date. (Because I don't know of any other particular recommendation.)
> Note that if a standard allows a name to be specified as a URI (which
> most of the SWE standards do, yes?), that is another place where the
> sensor web.
>
>
> Can you point me to any specific examples (i.e., URLs to files)?
>
> I'm having some difficulty seeing how a *relationship*, like
> 'dataset=OMI_A_G' can be expressed with the xlink or URI...
>
> Thx,
>
>
>
> On Jul 15, 2009, at 12:53 PM, Christopher Lynnes wrote:
>
> Greetings!
>
> Over in the Air Quality Cluster, we are experimenting with using
> some kind of structured markup / tagging of OGC WMS and WCS
> capabilities documents (inside <Keyword> elements) to allow us to do
> structured searches on the documents. An example might be, "give me
> the layers where Dataset = 'OMI_AI_G'". Seehttp://wiki.esipfed.org/index.php/WMS_GetCapabilities#WMS_GetCapabilities_Layer_Description
>
> Thing is, we figure if we are going to try to implement this kind of
> markup with a quasi-controlled vocabulary, we should do it in such a
> way that it is compatible with or even leverages the semantic web.
> We have pondered a machine tags approach, e.g.,
> <Keyword>esip:dataset=OMI_AI_G</Keyword>. (A link to an initial
> attempt of a WMS that includes the current keyword encoding: http://webapps.datafed.net/AIRNOW.ogc?service=wms&request=getCapabilities&version=1.1.1)
> .
>
> Alternatively, we have heard RDFa mentioned for microformats, though
> mostly in the context of XHTML. Can this be applied to OGC's XML
> and if so, how?
>
> Can the ESIP Semantic Web cluster provide a recommendation or
> suggestion in how to move forward that would be:
> (a) flexible and extensible,
> (b) compatible with the evolving ESIP datatype and services ontology
> and
> (c) lightweight and easy to use?
> --
> Christopher Lynnes NASA/GSFC, Code 610.2
> 301-614-5185
>
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>
>
> John
>
> --------------
> John Graybeal <mailto:graybeal at mbari.org> -- 831-775-1956
> Monterey Bay Aquarium Research Institute
> Marine Metadata Interoperability Project: http://marinemetadata.org
>
>
> --
> Christopher Lynnes NASA/GSFC, Code 610.2
> 301-614-5185
>
> _______________________________________________
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> esip-semanticweb at rtpnet.org
> http://lists.deltaforce.net/mailman/listinfo/esip-semanticweb
>
>
>
> --
> Dr. M. Benno Blumenthal benno at iri.columbia.edu
> International Research Institute for climate and society
> The Earth Institute at Columbia University
> Lamont Campus, Palisades NY 10964-8000 (845) 680-4450
> _______________________________________________
> esip-semanticweb mailing list
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>
>
> John
>
> --------------
> John Graybeal <mailto:graybeal at mbari.org> -- 831-775-1956
> Monterey Bay Aquarium Research Institute
> Marine Metadata Interoperability Project: http://marinemetadata.org
>
>
> --
> Christopher Lynnes NASA/GSFC, Code 610.2
> 301-614-5185
>
>
>
>
> --
> Dr. M. Benno Blumenthal benno at iri.columbia.edu
> International Research Institute for climate and society
> The Earth Institute at Columbia University
> Lamont Campus, Palisades NY 10964-8000 (845) 680-4450
--
Christopher Lynnes NASA/GSFC, Code 610.2
301-614-5185
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