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Use cases wrt Dataset proposal (UC 1.5, UC 5.2)

From: Antoine Zimmermann <antoine.zimmermann@emse.fr>
Date: Wed, 29 Feb 2012 15:43:15 +0100
Message-ID: <4F4E3983.9030508@emse.fr>
To: RDF WG <public-rdf-wg@w3.org>
*Beware*: this is about design solutions using the dataset proposal as a 
whole. It is not strictly related to the semantics. It explains 
concretely how one could store things in a dataset, possibly entail new 
things according the dataset semantics of [2] and so on, such that 
eventually it addresses the use case. So it contains a number of things 
that applications should do to address the UCs, independently of the 
truth values of triples or "named" graphs.


UC 1.5: Exchanging the contents of RDF stores

This is trivial. RDF stores mostly implement SPARQL datasets, so it 
suffices to have a serialisation syntax for datasets. It does not matter 
what the semantics is. TriG or N-Qauds will do.


UC 5.2: OWL's “Ontology Documents”

Currently, OWL imports statement means that an OWL processor should 
fetch wathever document it founds when "accessing" the imported URI 
(using whatever protocol it needs, see [1]). This behaviour is 
independent of the formal semantics of OWL ontologies. It's an operation 
that must be done prior to any interpretation of the ontology.

If multiple ontologies are stored in a dataset, it seems reasonable to 
use the import mechanism offline, where instead of a HTTP lookup, the 
system directly fetches from the corresponding "named" graph. This 
behaviour is not covered by the semantics of [2], but the notion of 
dataset as a syntactic structure makes it easy to define.

A design solution relying on quads would be possible too, by stating 
that an ontology which imports X also contains all the RDF statements 
that can be extracted from quads having X as a fourth element. But I 
find this formulation a bit convoluted compared to the formulation which 
uses datasets as a data structure.

This means that owl:imports defines a constraint on possible 
interpretations of a dataset. Especially, it means that, considering a 
dataset interpretation I = (Id, I1, ..., Ik) of a dataset D = 
(G,<n1,G1>,...,<nk,Gk>), if a graph Gi has an import statement:

  <Gi> owl:imports <Gj>

then the interpretation Ii must satisfy Gj as well as Gi. If two graphs 
are not related with an import relation, then the two graphs would still 
be interpreted as two completely disjoint theories.



[1] http://www.w3.org/TR/2009/REC-owl2-syntax-20091027/#Ontology_Documents
[2] 
http://www.w3.org/2011/rdf-wg/wiki/TF-Graphs/RDF-Datasets-Proposal#Semantics
-- 
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 83 36
Fax:+33(0)4 77 42 66 66
http://zimmer.aprilfoolsreview.com/
Received on Wednesday, 29 February 2012 14:43:42 UTC

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