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Re: Transforming RDF into (non-binary!) trees

From: Eric Prud'hommeaux <eric@w3.org>
Date: Mon, 7 Jul 2014 09:49:52 -0400
To: Paul Tyson <phtyson@sbcglobal.net>
Cc: Victor Porton <porton@narod.ru>, semantic-web@w3.org
Message-ID: <20140707134950.GB19116@w3.org>
* Paul Tyson <phtyson@sbcglobal.net> [2014-07-06 10:46-0500]
> On Sat, 2014-07-05 at 22:35 +0300, Victor Porton wrote:
> > I think we should write some code which would transform RDF into a tree
> >  (not necessarily binary! utilize nameless nodes as nodes with N
> >  childs) and also check the number of branches of a certain kind
> >  (usually 0..1 or 1..1).
> > 
> > Has anyone done a similar job?
> 
> I have not done that in RDF, but recently I had to generate optimal
> spanning trees [1] from a directed acyclic graph (DAG). It occurred to
> me that a similar technique could be applied to RDF if you first omitted
> cycles from the RDF graph (perhaps by introducing blank nodes).
> 
> One approach would be to put the spanning tree (however you choose to
> define it) in one named graph, and all the other "non-tree" triples in
> another named graph.
> 
> This would make it easier to apply conventional block-and-line layout
> styles (using XSL or CSS) to the spanning tree, and use the non-tree
> links to "decorate" the format (e.g. using hyperlinks or other
> interactive behavior).
> 
> Your use case might be quite different than mine. I am motivated by the
> problem of applying formatting style to RDF graphs. Since conventional
> layout techniques for screen and paper have a tree-based target model
> (pages/screens,blocks,lines,characters), somewhere in the process you
> must find or make a tree from your graph-based data. By specifying how
> to construct one or more useful (i.e., "meaningful for formatting")
> spanning trees from a given RDF graph, you achieve greater flexibility
> and transparency in the process.

I have a similar use case where I'm using ShEx semantic actions to map
large RDF documents like
  <http://www.w3.org/2013/C-CDA/IJ.xml> (needs CSS to render as Turtle)
into XML or JSON trees. A terse example of this is at
  <http://www.w3.org/2013/ShEx/FancyShExDemo?schemaURL=test/GenX/schema.shex&dataURL=test/Issue-pass-date.ttl>
(Look for "View GenX output as" to render XML.)
Does this approach your to-tree use case (albeit a different tree language)?


> I suppose such a system could be implemented with SPARQL, but it would
> be nice to have a non-SPARQL declarative syntax for specifying the
> spanning tree. RIF might work.
> 
> Regards,
> --Paul
> 
> [1] http://en.wikipedia.org/wiki/Spanning_tree
> 
> > 
> > I am working for bindings librdf for Ada2012. I could write such code
> >  directly in Ada (so it may be easier), but better would be to make C
> >  interface for this. I may write in Ada and leave TODO note "port it to
> >  C".
> > 
> > Any response?
> > 
> > --
> > Victor Porton - http://portonvictor.org
> > 
> 
> 
> 

-- 
-ericP

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Received on Monday, 7 July 2014 13:50:00 UTC

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