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Re: dataset syntax metadata

From: Antoine Zimmermann <antoine.zimmermann@emse.fr>
Date: Thu, 27 Sep 2012 11:23:02 +0200
Message-ID: <50641AF6.2050606@emse.fr>
To: public-rdf-wg@w3.org
CC: lee@thefigtrees.net
Lee,


Le 26/09/2012 18:50, Lee Feigenbaum a écrit :
> I'm not sure if this is at all helpful input, but here's how we handle
> metadata -- in general -- in Anzo. Pat, you may avert your eyes because
> the semantics are inconsistent at best.

There is no accepted semantics for dataset, so your safe with 
consistency at the moment.

BTW, the semantics at:
http://www.w3.org/2011/rdf-wg/wiki/TF-Graphs/Minimal-dataset-semantics
and at
http://www.w3.org/2011/rdf-wg/wiki/index.php?title=TF-Graphs/Minimal-dataset-semantics&oldid=2438
and at
http://www.w3.org/2011/rdf-wg/wiki/TF-Graphs/RDF-Datasets-Proposal#Semantics

all make your datasets consistent.


>
> A couple of "regular" named graphs
>
> <p1> { <p1> a ex:Person ; foaf:name "Lee" ... }
> <p2> { <p2> a ex:Person ; foaf:name "Lynn" ... }
>
> Named graphs have corresponding "metadata" graphs
>
> <mdg1> { <mdg1> a anzo:MetadataGraph . <p1> a anzo:NamedGraph ;
> anzo:hasMetadataGraph <mdg1> ; anzo:createdBy ... ; anzo:lastModifiedBy
> ... ; anzo:lastModifiedAt ... ; ... }
> <mdg2> { <mdg2> a anzo:MetadataGraph . <p2> a anzo:NamedGraph ;
> anzo:hasMetadataGraph <mdg2> ; anzo:createdBy ... ; anzo:lastModifiedBy
> ... ; anzo:lastModifiedAt ... ; ... }
>
> We also have first-class datasets, that are represented roughly like:
>
> <ds1> { <ds1> a anzo:Dataset ; anzo:hasDefaultGraph <p1> ;
> anzo:hasNamedGraph <p1>, <p2> }
>
> Of course, <ds1> is also a regular named graph, so there's a
> corresponding metadata graph with metadata about the dataset:
>
> <mdg3> { <mdg3> a anzo:MetadataGraph . <ds1> a anzo:NamedGraph ;
> anzo:hasMetadataGraph <mdg3> ; anzo:createdBy ... ; anzo:lastModifiedBy
> ... ; anzo:lastModifiedAt ... ; ... }
>
> Among other things, we use these datasets directly within SPARQL by
> extending SPARQL with a FROM DATASET clause:
>
> SELECT ...
> FROM DATASET <ds1>
> WHERE { ... }
>
> ...which would be equivalent in this example to
>
> SELECT ...
> FROM <p1>
> FROM NAMED <p1>
> FROM NAMED <p2>
> WHERE { ... }
>
> When we import TriG, we generally are just doing either a replace or an
> add on the data in the named graphs in the TriG file. We generally don't
> automatically create anzo:Dataset's based on the contents of a
> particular TriG file. Instead, if we were exporting and then importing a
> dataset, we'd just include the <ds1> graph in our export so we'd have it
> back again in an import in the future.
>
> Regarding your question (a), Sandro, you can always find the metadata
> graph for a particular graph (including a dataset graph) simply by
> querying for the anzo:hasMetadataGraph triple.

How would you do that? If I do:

SELECT ?mdg WHERE {
   ?mdg  a  anzo:hasMetadataGraph .
}

this should query the default graph, which is non existent, or defined 
specifically per datasets. So how does it work exactly?


<skip/>

-- 
Antoine Zimmermann
ISCOD / LSTI - Institut Henri Fayol
École Nationale Supérieure des Mines de Saint-Étienne
158 cours Fauriel
42023 Saint-Étienne Cedex 2
France
Tél:+33(0)4 77 42 66 03
Fax:+33(0)4 77 42 66 66
http://zimmer.aprilfoolsreview.com/
Received on Thursday, 27 September 2012 09:23:36 GMT

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