W3C home > Mailing lists > Public > public-xg-ssn@w3.org > August 2009

Re: Survey paper

From: John Graybeal <graybeal@mbari.org>
Date: Thu, 13 Aug 2009 17:50:21 -0700
Message-Id: <56ABA394-8848-4465-B60C-72DF2B2EE04F@mbari.org>
To: public-xg-ssn@w3.org
This exchange reminds me...

At the last telecon statements were made about the agreed goal(s) of  
the semantic markup activity.  I can find no reference to these goals  
in the charter, which explicitly says that goals not in the charter  
are not to be addressed.

So, can someone please amend the charter to be correct with regard to  
the semantic markup goals? Or at least send a statement of those goals  
to the list, so that we are all on the same page?

John

On Aug 13, 2009, at 9:18 AM, Luis Bermudez wrote:

> Cory,
>
> I think the end goal is to take SOS responses and transform those to  
> RDF. Meaning, we need to create a graph with triples  composed of  
> Resource/ Property values. And, as we know Resources and Properties  
> need be represented via URIs. Values can take a URI or a literal  
> value. So, we  need to identify in SensorML and O&M  place holders  
> for URIs. And we should use those as starting point when building  
> our graph. For example, UML properties, xpath pointing to xlink  
> attibutes, xpaths pointing to XML elements ( like the one I  
> described in a previous email),  or in the future GML identifiers.
>
> So... xlink is just one avenue..
>
> -luis
>
>
> On Thu, Aug 13, 2009 at 11:41 AM, Simon Cox <simon.cox@jrc.ec.europa.eu 
> > wrote:
> (1) If the point is to illustrate use of xlink for annotations, then  
> you need to make sure that the example really does use xlink for  
> this purpose.
> I'm not convinced that authorized GML xlink:*href* usage does this.
>
> xlink:role and xlink:arcrole might be OK, but there are very few  
> examples in real-life (see https://www.seegrid.csiro.au/twiki/bin/view/AppSchemas/ObservationsAndSampling 
> #Unknown_features for a pattern that has been used in the geoscience  
> community).
>
> (2) As mentioned in my PS below, XLink has barely been implemented.
> So XLink semantics are essentially bound to to the small number of  
> contexts where it has actually been used.
> RDDL and GML could be the most significant users (and yes, folks,  
> GML is now seeing significant deployment, particularly under the  
> auspices of GeoSciML/oneGeology and INSPIRE) so my story could be as  
> good as it gets ...
>
> Simon
>
>
> Simon Cox
>
> European Commission, Joint Research Centre,
> Institute for Environment and Sustainability,
> Spatial Data Infrastructures Unit, TP 262
> Via E. Fermi, 2749, I-21027 Ispra (VA), Italy
> Tel: +39 0332 78 3652
> Fax: +39 0332 78 6325
> mailto:simon.cox@jrc.ec.europa.eu
> http://ies.jrc.ec.europa.eu/simon-cox
>
> SDI Unit: http://sdi.jrc.ec.europa.eu/
> IES Institute: http://ies.jrc.ec.europa.eu/
> JRC: http://www.jrc.ec.europa.eu/
>
>
>
> From: public-xg-ssn-request@w3.org [mailto:public-xg-ssn-request@w3.org 
> ] On Behalf Of Cory Henson
> Sent: Thursday, 13 August 2009 17:28
> To: Simon Cox
> Cc: Laurent.Lefort@csiro.au; Michael.Compton@csiro.au; public-xg-ssn@w3.org
> Subject: Re: Survey paper
>
> I think this is a good discussion that we should continue, but as  
> far as the survey paper is concerned there are two questions. (1)  
> Should this be included as an annotation technique? There seems to  
> be several groups using xlink as a 'model reference to an  
> ontological description,' including also MMI/OOTethis (whether this  
> is right or wrong, and these were discussed in ssn-xg meeting).  And  
> second, (2) does XLink have a predefined translation to RDF (in  
> rough equivalence to RDFa)?  And be aware we only have one page for  
> this topic in the survey.
>
> thanks,
> -Cory
>
> On Thu, Aug 13, 2009 at 11:00 AM, Simon Cox <simon.cox@jrc.ec.europa.eu 
> > wrote:
> PS - the whole xlink (and also xpointer) story is rather sad.
> Going back to the dawn of XML (1997 or thereabouts in public forums)  
> the XML spec was supposed to have three legs:
> XML Syntax
> XML Linking
> XML Transformations.
>
> Xlink was the last to emerage, and has barely been implemented  
> anywhere.
> Which is a shame because linking is the basis of the web.
> And in the absence of a consensus on linking semantics, we are still  
> having discussion like this.
>
> Similarly xpointer - it is supposed to augment URI syntax by  
> allowing XPath expressions to point to fragments of resources - with  
> a special escape clause for # pointers which have gone by various  
> names.
>
> We were perhaps over-eager/premature to adopt these technologies in  
> the GML spec (Laurent's EXAMPLE 3 below was my attempt to use the  
> current state of the confusing xpointer documentation). But the  
> defense is that if we had not adopted these external specs, we'd  
> have had to invent something with similar semantics ourselves. So we  
> took the lazy programmers route and used something already available  
> (!) that looked right.
>
>
> Simon Cox
>
> European Commission, Joint Research Centre,
> Institute for Environment and Sustainability,
> Spatial Data Infrastructures Unit, TP 262
> Via E. Fermi, 2749, I-21027 Ispra (VA), Italy
> Tel: +39 0332 78 3652
> Fax: +39 0332 78 6325
> mailto:simon.cox@jrc.ec.europa.eu
> http://ies.jrc.ec.europa.eu/simon-cox
>
> SDI Unit: http://sdi.jrc.ec.europa.eu/
> IES Institute: http://ies.jrc.ec.europa.eu/
> JRC: http://www.jrc.ec.europa.eu/
>
>
>
> From: Simon Cox [mailto:simon.cox@jrc.ec.europa.eu]
> Sent: Thursday, 13 August 2009 16:52
> To: 'Laurent.Lefort@csiro.au'; 'coryhenson@gmail.com'
>
> Cc: 'Michael.Compton@csiro.au'; 'public-xg-ssn@w3.org'
> Subject: RE: Survey paper
>
> Thanks Laurent - I think your analysis is fairly complete.
>
> Regarding
>
> > "Property metadata in GML ... overloading href, and use of other  
> xlinks" = 'model reference to a ontological description'
> > https://www.seegrid.csiro.au/twiki/bin/view/AppSchemas/PropertyMetadata
>
> This was a proposal of mine, and does not yet have any formal status.
> It was submitted to the currently active GML working group, but has  
> not been discussed yet.
>
> So 'composition by inclusion of remote resources'  is currently the  
> only authorized use of xlinks in GML.
>
> Simon Cox
>
>
>
> European Commission, Joint Research Centre,
> Institute for Environment and Sustainability,
> Spatial Data Infrastructures Unit, TP 262
> Via E. Fermi, 2749, I-21027 Ispra (VA), Italy
> Tel: +39 0332 78 3652
> Fax: +39 0332 78 6325
>
>
> mailto:simon.cox@jrc.ec.europa.eu
> http://ies.jrc.ec.europa.eu/simon-cox
>
> SDI Unit: http://sdi.jrc.ec.europa.eu/
> IES Institute: http://ies.jrc.ec.europa.eu/
> JRC: http://www.jrc.ec.europa.eu/
>
>
> From: public-xg-ssn-request@w3.org [mailto:public-xg-ssn-request@w3.org 
> ] On Behalf Of Laurent.Lefort@csiro.au
> Sent: Thursday, 13 August 2009 16:39
> To: simon.cox@jrc.ec.europa.eu; coryhenson@gmail.com
>
> Cc: Michael.Compton@csiro.au; public-xg-ssn@w3.org
> Subject: RE: Survey paper
>
> Hi Cory,
>
> This is one of the trickiest parts of the paper. I'm on a steep  
> learning curve for RDFa and have scracthed my head before on xlink  
> before but I'll try to help.
>
> The way I would put it is:
>
> 1) xlink is almost the semantic equivalent in XML to void* pointers  
> in C programs - when you got one, you're not always sure what you  
> can do with it because the valid recipe to handle it will depends on  
> the subset of xlink use cases which are allowed (similarily, how to  
> deal with void* in C programs depends largely on the age of the  
> captain. So, any solution which does not propagate it is preferable.
>
> 2) If you have to use it, you need to look at the fine print to  
> check what the specs says:
>
> For example, in SVG, the xlink usage is described here: http://www.w3.org/TR/SVG/linking.html
>
>
> 3) In my opinion, the GML usage of xlink is incompletly described in  
> Section 8 of http://portal.opengeospatial.org/files/?artifact_id=20509
>
> Simon and other OGC colleagues posting on the seegrid wiki have  
> documented the xlink usage in GML in 2006 in two wiki pages which  
> corresponds to the two different use cases I think you are talking  
> about:
>
> 'model reference to a ontological description' vs 'composition by  
> inclusion of remote resources'
>
> I think that:
> GML Implementation of Features and Properties = 'composition by  
> inclusion of remote resources'
> https://www.seegrid.csiro.au/twiki/bin/view/AppSchemas/GmlImplementation
>
> and:
> "Property metadata in GML ... overloading href, and use of other  
> xlinks" = 'model reference to a ontological description'
> https://www.seegrid.csiro.au/twiki/bin/view/AppSchemas/ 
> PropertyMetadata
>
> The major difficulty you should be aware of is that there are  
> several (subtly) different usages in of xlinks in usage in sub- 
> communities of OGC:
> Xlink can be used to point to "fragment" of other XML or HTML files  
> (locatable through a # beacon   declaration or with the help of   
> Xpath expression)
>
> The GML spec authorises 4 variants:
> EXAMPLE 1 A reference to an object element in the same GML document  
> may be encoded as:
>
> <myProperty xlink:href="#o1"/>
>
> EXAMPLE 2 A reference to an object element in a remote XML document  
> using the gml:id value of that object may be encoded as:
>
> <myProperty xlink:href="http://my.big.org/test.xml#o1"/>
>
> EXAMPLE 3* A reference to an object element in a remote XML document  
> (or GML object repository) using the gml:identifier property value  
> of that object may be encoded as:
>
> <myProperty xlink:href="http://my.big.org/test.xml#element(// 
> gml:GeodeticCRS[./gml:identifier[@codeSpace="urn:x-ogc:def:crs:EPSG:6.3 
> :"]="4326"])"/>
>
> *Personally, I have never seen anyone which uses this XPath  
> augmented style of uris ...
>
> EXAMPLE 4 A reference to an object element with a uniform resource  
> name may be encoded as follows (note that a URN resolver is required  
> to resolve the URN and access the referenced object):
>
> <myProperty xlink:href="urn:x-ogc:def:crs:EPSG:6.3:4326"/>
>
> These 4 examples correspond to a first case of  'composition by  
> inclusion of remote resources'
>
> One issue is that the GML specification let the door open to all the  
> possibility defined by the XLink   spec through this sentence "the  
> most useful of these [xlink attributes] are" .... and "For complete  
> definitions of these and other Xlink components, including their use  
> in extended Xlink association maps, refer to the Xlink specification."
>
> This GML xLink Profile (07-083) by Andrew Woolf http://epubs.cclrc.ac.uk/bitstream/1851/AWO%20-%20xlink.ppt 
>  describes how some of these xlink attributes should be used in GML  
> for a small sets of specific use cases. It has also been proposed  
> around 2006 but to my knowledge it has not been approved or recyled  
> in a formally approved GML spec. probably because it corresponds to  
> a specific use case, when xlink are used to locate resources  
> embedded in netCDF files.
>
>
> I have to rush a bit here because you have exchanged 3 messages  
> since I have started to type.
>
> I think that the usage of xlink in SWE may be different and = 'model  
> reference to a ontological description'
>
> This is a different case because the xlink pointer is no longer used  
> to point to something which would corresponds to a RDF instance  
> (container of data) but rather to what would be a property of a  
> class in the ontology (or in a UML model).
>
> 4) Different types of URIs
>
> Long story (another post needed). For better scoped definitions, see  
> the skos notation or the CURIEs spec.
>
> 5) Source of confusion (in general and in the paper)
>
> There are many possible combinations of the above usage. You are  
> introducing a new one which is to use xlink for annotations.
>
> Question: do you want to attach an annotation to a block of XML file  
> which could have been replaced by a xlink pointer for the purpose of  
> 'composition by inclusion of remote resources'  (e.g a gml:Point) or  
> a block of the XML file which is a  'model reference to a  
> ontological description' vs 'composition by inclusion of remote  
> resources'
> (e.g. a swe:Phenomenon). I think to you should have different  
> mappings for the two cases.
>
> 6) To be continued ...
>
> Laurent.
>
> PS: The GML spec says page 20:  GML follows RDF (W3C, 1999)  
> terminology and uses the term property rather than attribute or  
> association role.
> This translates to something like: some of the names of class or  
> attributes used in GML have been borrowed from RDF.
>
> But not to something like: When the user find a RDF-like concept in  
> GML, he can be confident that the semantics of the corresponding  
> concept or role in the RDF specs are applicable to it.
>
>
> From: public-xg-ssn-request@w3.org [mailto:public-xg-ssn-request@w3.org 
> ] On Behalf Of Cory Henson
> Sent: Thursday, 13 August 2009 14:27
> To: Simon Cox
> Cc: Michael.Compton@csiro.au; public-xg-ssn@w3.org
> Subject: Re: Survey paper
>
> Hi Simon,
>
> Thanks for the comment.  We are using the term semantic annotation  
> as described in SAWSDL, as a model reference to a ontological  
> description.  Does this conflict with the description as a  
> 'composition by inclusion of remote resources'? As far as mapping to  
> RDF, this is in comparison to RDFa which has a known syntactic  
> translation from the set of annotations to RDF triples. While  
> xlink:href maps to rdf:resource, how would the values of properties  
> of this resource be translated to RDF? If this is not correct, or  
> the wording is awkward, please point us in the right direction.   
> Thanks for your help.
>
> -Cory
>
>
> On Thu, Aug 13, 2009 at 8:01 AM, Simon Cox  
> <simon.cox@jrc.ec.europa.eu> wrote:
> Hi Mike -
>
> A clarification relating to semantic annotations and xlink:
>
> In GML-style XML documents, xlink:href plays the same role as  
> rdf:resource
> in an RDF/XML document.
> I.e. it holds a pointer to external resource, which could be pasted  
> inline
> as an anonymous node with equivalent semantics.
> This is a basic GML pattern and is explained in the GML spec
> http://portal.opengeospatial.org/files/?artifact_id=20509 clause  
> 7.2.3.
> The examples involving xlink:href in Figure 2 aren't exactly  
> 'annotations',
> more 'composition by inclusion of remote resources'.
>
> So I'm not sure if the example supports the point you are making.
>
> You comment 'XLink has no predefined mapping to RDF.'
> As mentioned above, _as used in GML documents_ xlink:href maps to
> rdf:resource.
>
> Simon Cox
>
> European Commission, Joint Research Centre,
> Institute for Environment and Sustainability,
> Spatial Data Infrastructures Unit, TP 262
> Via E. Fermi, 2749, I-21027 Ispra (VA), Italy
> Tel: +39 0332 78 3652
> Fax: +39 0332 78 6325
> mailto:simon.cox@jrc.ec.europa.eu
> http://ies.jrc.ec.europa.eu/simon-cox
>
> SDI Unit: http://sdi.jrc.ec.europa.eu/
> IES Institute: http://ies.jrc.ec.europa.eu/
> JRC: http://www.jrc.ec.europa.eu/
>
> -----Original Message-----
> From: public-xg-ssn-request@w3.org [mailto:public-xg-ssn-request@w3.org 
> ] On
> Behalf Of Michael.Compton@csiro.au
> Sent: Thursday, 13 August 2009 13:43
> To: public-xg-ssn@w3.org
> Subject: Survey paper
>
> Hi all,
>
> Sorry it's so close to the SSN'09 deadline, but with help from Cory  
> and
> Holger, I (finally) have a survey paper.  Please read, comment, etc.
>
> (there are a couple of obvious tweaks/FIXME's yet to be made)
>
> Michael
>
>
>
>
>
> -- 
> Cory Andrew Henson
> Kno.e.sis Center, Wright State University
> http://knoesis.wright.edu/researchers/cory/
>
>
>
> -- 
> Cory Andrew Henson
> Kno.e.sis Center, Wright State University
> http://knoesis.wright.edu/researchers/cory/
>
>
>
> -- 
> Luis Bermudez Ph.D.
> Coastal Research Technical Manager
> Southeastern Universities Research Association (SURA)
> bermudez@sura.org - Office: (202) 408-8211
> 1201 New York Ave. NW Suite 430, Washington DC 20005


--------------
NOTE NEW EMAIL ADDRESS
--------------
John Graybeal   <mailto:jbgraybeal@mindspring.com>
Marine Metadata Interoperability Project: http://marinemetadata.org
Received on Friday, 14 August 2009 00:51:17 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Friday, 14 August 2009 00:51:18 GMT