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RE: Building a bridge from RDF to the web?

From: Seaborne, Andy <andy.seaborne@hp.com>
Date: Tue, 25 May 2004 13:27:45 +0100
Message-ID: <E864E95CB35C1C46B72FEA0626A2E808031A98A7@0-mail-br1.hpl.hp.com>
To: "Thompson, Bryan B." <BRYAN.B.THOMPSON@saic.com>, "''public-rdf-dawg@w3.org' '" <public-rdf-dawg@w3.org>



-------- Original Message --------
> From: Thompson, Bryan B. <mailto:BRYAN.B.THOMPSON@saic.com>
> Date: 25 May 2004 13:13
> 
> Andy,
> 
> You wrote:
> 
> > If that bridge is a way to extract information from RDF models and
> > get it into both XHTML (for people) and XML (for people and for
> > web services), then I agree with you.
> 
> Variable bindings certainly seem to be a good place to start in order
> for the client to be able to avoid posing the query twice - once to
> the RDF store and once to the identified sub-graph (and possible using
> a different kind of query interface altogether!)
> 
> So, can you outline for me how you see that variable bindings exposed
> by a DAWG protocol could be exploited by an XML Stylesheet so as to
> generate, e.g., an XHTML document?
> 
> -bryan

Rather than an on-the-fly design, how about from the examples of systems
that have tried this:

---------------------

From: http://rdfweb.org/people/damian/treehugger/introduction.html
Treehugger example:

<xsl:for-each 
  select="./rss:items/rdf:Seq/rdf:li/rdf:Resource">
     ...
     do something with each member of the sequence
     ...
</xsl:for-each>

A path is Treehugger is property/class/property/class - I prefer a
property/property/property path but that isn't relevant here.

So make/replace the "select" attribute be a graph pattern.  Need to cope
with multiple variables in the query string.

---------------------

From Jonathan Robie's talk:
http://www.w3.org/2004/Talks/tp-robie/slide4-0.html

declare namespace rdf = "rdf.tagsalad.org";

for $artist in rdf:instance-of-class(rdf:predicate-domain("c:creates"))
let $artifact := rdf:join-on-property($artist, "c:creates"),
    $museum := rdf:join-on-property($artifact, "c:exhibited")
return 
    <result>
       <artist>{ $artist }</artist>
       <artifact>{ $artifact }</artifact>
       <museum>{ $museum }</museum>
    </result>

---------------------

Can one write in Xquery:
   $var1 $var2 := someQueryFunction("graph pattern")
If so, then this would be a more compact form.

Bryan - is this what you had in mind?

	Andy



> 
> -----Original Message-----
> From: Seaborne, Andy
> To: Thompson, Bryan B.; 'public-rdf-dawg@w3.org'
> Sent: 5/25/2004 6:39 AM
> Subject: RE: Building a bridge from RDF to the web?
> 
> > From: Thompson, Bryan B. <>
> > Date: 24 May 2004 20:49
> > 
> > One of the issues that became clear to me during the recent WWW
> > meeting in NYC is that we are missing a bridge between the RDF model
> > and XML. In particular, people who are going to be using the semantic
> > web need a bridge from the RDF data model to application specific XML
> > vocabularies (actually, we need one that goes the other way also, but
> > that is, I think, a seperate question).  Perhaps the most common use
> > case is querying an RDF resource and using the results to drive an XSL
> > Transform, which in turn might generate XHTML.
> 
> If that bridge is a way to extract information from RDF models and get
> it
> into both XHTML (for people) and XML (for people and for web services),
> then
> I agree with you.  There isn't going to be one such form for presenting
> information extracted from RDF so tools such as XSLT and XQuery seem to
> be
> the toolsets to use.
> 
> There has been some work on this: Rob outlined the use of XQuery and OWL
> data, and it reminded me of Jonathan Robie's presentation [1] at Cannes
> this
> year.  The important aspect here is that access is to the abstract
> graph,
> not the RDF/XML syntax.
> 
> Elsewhere, Howard talked about using paths to access the graph and
> Treehugger [2] does this by dymanically materialising an XML document
> from
> the RDF abstract graph.
> 
> This is getting stuff out of RDF.  The requirement it places on the WG,
> as I
> see it, is to produce a format for variable bindings that is easily
> digestable by other systems.  That does not automatically mean an XML
> format
> because it is the output of XQuery functions but an XML format would
> work
> (it can be made streamable which RDF isn't).
> 
> I have also seem people do queries in JSP taglibs to produce HTML and
> also
> using Velocity to create XHTML from RDF - a standard library to do the
> variable bindings to Velocity
> 
> > 
> > This issue has been more or less discussed in the context of
> > templates, which did not receive strong support at the first f2f as a
> > requirement for DAWG.
> 
> IIRC the "Templates" discussion was slightly different.  Its about
> constructing new RDF from information pulled from existing RDF.  See the
> SeRQL 'construct' [3] operation or "cwm --filter".
> 
> >  However I think that NOT having this is going to be a major
> > stumbling block for adoption of the DAWG recommendation by application
> > developers and is going to make it very difficult to get at that sense
> > of loose coupling and content reuse that makes the web so exciting.
> > 
> > I would like to get a sense from people of how a DAWG spec could best
> > facilitate this.  Do we need to do this ourselves?  Can we expose the
> > data model query language in such a way that it can be usefully
> > applied by XSL Transforms?  Should this be considered out of scope
> > for the charter? 
> > 
> > Thanks,
> > 
> > -bryan
> 
> [1] http://www.w3.org/2004/Talks/tp-robie/
> [2] http://rdfweb.org/people/damian/treehugger/
> [3] http://www.openrdf.org/doc/users/ch05.html#d0e1101
Received on Tuesday, 25 May 2004 08:28:22 GMT

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