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Re: XPATH for RDF ?

From: Steve Cassidy <Steve.Cassidy@mq.edu.au>
Date: Tue, 21 Oct 2003 21:33:05 +1000
Message-ID: <3F951971.5010101@mq.edu.au>
To: leo@gnowsis.com
Cc: www-rdf-interest@w3.org

Leo Sauermann wrote:

>Is there a project that does a thing similiar to "XPATH" for RDF ?
>....
>
>So XML parsing won't work, we need a XPATH-thing that has a RDF graph as
>a basis for data querying.
>
>  
>
I presented some work at Extreme Markup this year on Generalising XPath
for Directed Graphs [1], one use case of which is obviously RDF although
the original design goals were in a different domain.

The two main generalisations are to allow arbitrary axis definitions (as 
mappings from nodes to node sets) and to allow conditions to be placed 
on paths as well as on nodes. In RDF I ended up with a path syntax where 
each step looks like:
 
predicate{step}::TypeOrLiteral[predicate]::{where}

predicate is an RDF predicate, TypeOrLiteral is (guess what) either an 
rdf:type or a literal. step is a specifcation of how many steps to take 
along the axis (defined here by the transitive closure of a predicate) 
and where is a specification of where the node test applies (eg. on all 
nodes, just at the end or on the third and last nodes).

I'll leave an example to the paper since this is getting too verbose.

[note that this application to RDF was made up without deep thought and 
could perhaps be done better within the generalised xpath framework].

Any feedback would be welcome. I'm now looking at applying something 
like this to a task not unlike transforming RDF to XML and I'd like to 
explore the application to RDF some more.

Steve

[1] 
http://www.idealliance.org/papers/extreme03/html/2003/Cassidy01/EML2003Cassidy01-toc.html
Received on Tuesday, 21 October 2003 07:58:57 GMT

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