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   RE: Research notebook: On edge-labelled graphs in XML

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  • From: Michael Rys <mrys@microsoft.com>
  • To: "'tpassin@home.com'" <tpassin@home.com>, xml-dev@xml.org
  • Date: Wed, 06 Sep 2000 23:36:11 -0700

This is an interesting observation. As a proponent of edge-labelled graphs
(Lore, proposed XML data model based on edge-labelled graphs about a year
ago) I would favor this, however, due to the extensive node-centric models
within the W3C (DOM, XPath, but not the Infoset which should be interpreted
as agnostic on this), the current working draft is (in my personal and
humble opinion unfortunately) also node-labelled...

Best regards

> -----Original Message-----
> From: tpassin@home.com [mailto:tpassin@home.com]
> Sent: Wednesday, September 06, 2000 6:55 PM
> To: xml-dev@xml.org
> Subject: Re: Research notebook: On edge-labelled graphs in XML
> Dan Brickley asked about work on edge-labeled graphs as they 
> might be used
> in XML-related applications.
> >
> > So I'm posting a far-from-ready document since I expect RDF 
> Issues to eat
> > a bunch of time this month I might've spent on it:
> >
> > http://www.w3.org/2000/09/XGraph/
> > Research notebook: On edge-labelled graphs in XML
> >
> > ...on the basis that it's best to post half-finished but
> interesting/useful
> > material than sit on it for months hoping to perfect it (RDFViz,
> > RDF-WordNet etc being previous examples where I've gone 
> against instinct
> ;-)
> >
> >   "This document serves as an informal survey of XML 
> applications that
> adopt
> >    an edge-labelled graph data model similar to that used in W3C's
> Resource
> >    Description Framework (RDF)."
> I got interested in the edge-labeled approach after I read 
> "Data on the
> Web", by Abiteboul, Buneman, and Suciu.  From the book, it 
> appears that a
> lot of academic research on querying semi-structured data is 
> based on an
> edge-labeled approach. Since a query language for xml 
> documents is sorely
> needed, I thought it would be worth looking at the 
> edge-labeled approach a
> little more.   I came up with a way to represent XML documents by
> edge-labeled graphs - nodes are there mainly to allow for 
> containment of
> children or text values - PCDATA (text) can be imagined to be 
> contained in
> invisible <text>...</text> elements, so there are edges 
> labeled "text" too.
> The edges would contain the attributes, since edges represent 
> elements.
> This approach mapped closely to DTDs too - in the DTD the 
> nodes would be
> labeled with their multiplicity, and whether they were 
> alternations or not.
> Edges would not end in nodes since the DTD contains no actual 
> values.  Thus,
> a DTD graph appears remarkably similar to an actual instance graph.
> This was interesting and easy to set up.  I was able to write 
> rudimentary
> tree-building and xml-writing code very quickly (no, I didn't 
> include the
> whole infoset, I was just trying it out).  That's as much as 
> I've done to
> date, but it was stimulating.   It makes me think that the 
> subject is worth
> while.  But then we've got all those node-based models like 
> DOM, hate to
> reinvent all that stuff...
> Cheers,
> Tom Passin


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