Re: [GRAPHS] One graph to bind them all ?

> > In other words I believe we need to decide if there can be overlaps
> > between g-boxes, between g-snaps and between g-texts.
> >
> > I am convinced we need to allow overlapping g-boxes.
> > I am not too sure about overlapping g-snaps and overlapping g-texts.
> 
> What do existing systems do?

The TriG Syntax doesn't specify a way to associate a triple to several graphs
http://www4.wiwiss.fu-berlin.de/bizer/TriG/
More over it specifies that "Graph names must be unique within a TriG document."
So you can't split your named graph definition into several pieces.

We have a similar limitation on the "RDF/XML Source Declaration"
http://www.w3.org/Submission/rdfsource/
Using an attribute to name the current graph (lines 5 and 10):
01 <rdf:RDF xmlns:dc="http://purl.org/dc/elements/1.1/"
02  xmlns:foaf="http://xmlns.com/foaf/0.1/"
03  xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
04  xmlns:cos="http://www.inria.fr/acacia/corese#"
05  cos:graph="http://www.w3.org">
06 <rdf:Description rdf:about="http://www-sop.inria.fr/edelweiss/fabien/docs/w3c/rdfsource/rdfsource.html">
07  <dc:title>RDF Source</dc:title>
08  <dc:creator>
09    <foaf:Person rdf:about="http://ns.inria.fr/fabien.gandon/foaf#me" 
10      cos:graph="http://www.inria.fr" >
11     <foaf:name>Fabien Gandon</foaf:name>
12     <foaf:mbox rdf:resource="mailto:fgandon@inria.fr"/>
13   </foaf:Person>
14  </dc:creator>
15 </rdf:Description>
16 </rdf:RDF>

However in the past we encountered several use cases identifying the need for "overlapping identified graphs" in order to support multiple partitions of an RDF Dataset according to multiple points of view / dimensions.
e.g. http://www.w3.org/2011/rdf-wg/wiki/TF-Graphs-UC#Slicing_datasets_according_to_multiple_dimensions

As I understand the g-* notions, if a g-text is the serialization of a g-snap which is the capture of one g-box, then the question of overlapping g-box seems orthogonal since from outside the store one can only contemplate one g-box at a time through a g-text that was generated from it.

Now in an RDF document I can have several g-box serialized (a collection of g-texts?) and then the questions are:

- do I allow a triple to be part of several identified graphs for instance allowing several names to be specified and the same names to be reused?
e.g.
:G1,G2 { http://dbpedia.org/page/Nice geo:lat 43.703392 ; geo:long 7.266274 . }
:G1 { http://dbpedia.org/page/Nice ex:belongsTo http://dbpedia.org/page/France }
:G2 { http://dbpedia.org/page/Nice ex:belongsTo http://dbpedia.org/page/Italy }

- what should be the scope of a blank node in that context? the RDF document? the enclosing identified graph?
e.g.
:G1,G2 { _:a geo:lat 43.703392 ; geo:long 7.266274 . }
:G1 { _:a ex:belongsTo http://dbpedia.org/page/France }
:G2 { -:a ex:belongsTo http://dbpedia.org/page/Italy }

For now, my vote goes to allowing a triple to be part of several identified graphs and scoping the blank nodes to the RDF document.

Cheers,
--
fabien, inria, @fabien_gandon, http://fabien.info

Received on Wednesday, 2 March 2011 09:31:17 UTC