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Re: Reification and Provenance modelling

From: Bob Ferris <zazi@smiy.org>
Date: Thu, 15 Sep 2011 12:41:03 +0200
Message-ID: <4E71D63F.3050807@smiy.org>
To: public-rdf-comment@w3.org

I'm occasionally reading the RDF WG mailings re. Graph Task Force 
related topics. I have the feeling that there are not really great 
movements and that the existing proposals are not really getting the 
point (at least from my point view, e.g., I don't like graph literals at 
all). I still have the feeling that my proposal still could rule out all 
the other existing ones.
I would love to see this proposal discussed by the RDF WG Graph Task Force.

Thanks a lot in advance.



On 01/28/2011 08:18 PM, Bob Ferris wrote:
> Hi,
> since the new RDF WG is still forming, I thought it might be worth to
> bring up two issues re. reification and provenance modelling in here.
> 1. As I saw one issue on the new agenda is the standardization of the
> meaning of the forth element in quadruples. There might be a tendency
> that this should be used for referring the URI of a "named graph" (a set
> of triples, that means, hopefully more than one).
> However, currently I would rather tend to assign the forth element for
> an optional statement identifier, which is explicitly intended to be
> used for addressing provenance information. Provenance information is
> from my point of view 'external context' (cf. [1]) to information
> described in a semantic graph.
> The following example is also a response[2] of the question of how to do
> practical Named Graphs implementations[3]:
> This design allows triple (statement) identification over the enclosures
> of named semantic graphs and furthermore the treatment of provenance for
> statements and graphs in a same way. Additionally, the handling of n-ary
> relations, as an 'internal context' (cf. [1]) refinement of binary
> relation based descriptions, and its mapping to binary relations
> (property reification, see [4]).
> Here is an example, which was original only intended for representing
> the internal structure of a quad store. However this could also be used
> in a serialization format (cf. N-Quads [5], where the forth element is
> also optionally). I reformatted it to an N-Quad like serialization:
> <#alice> :friend <#bob> <#s1> . # a simple binary relation
> <#ab> rdf:type :HumanRelationship <#s2> ; # a property reification (an
> n-ary relation) related to the first binary relation
> <#ab> :participant <#alice> <#s3> ;
> <#ab> :participant <#bob> <#s4> ;
> <#ab> :relationshipType :friend <#s5> ;
> <#ab> :since "2010-12-12"^xsd:date <#s6> .
> <#s1> :reified <#ab> <#s7> ; # an inference that results in a
> reification relation (such a property currently does not exist, or?)
> <#g1> rdf:type rdfg:Graph <#s8> ; # a graph enclosure (which can also be
> more nicely serialized by the TriG syntax)
> <#g1> :contains <#s1> <s#9> ;
> <#g1> :contains <#s2> <#s10> ;
> <#g1> :contains <#s3> <#s11> ;
> <#g1> :contains <#s4> <#s12> ;
> <#g1> :contains <#s5> <#s13> ;
> <#g1> :contains <#s6> <#s14> ;
> <#g1> :contains <#s7> <#s15> .
> <#g2> rdf:type rdfg:Graph <#s16> ; # another graph enclosure
> <#g2> :contains <#s1> <#s17> .
> -> I can easily get all statements of a graph by using the :contains
> relation (indexing)
> -> I can easily get semantically related property-oriented context
> descriptions (n-ary relations) by using the :reified relation
> -> provenance on the statement and on the graph level can easily be done
> by describing the <#g*> and <#s*> information resources:
> - thereby, <#s9> - <s#15> and <s#17> are intended for describing
> provenance information of statement <#s*> in graph <#g*>
> - one can maybe also inherit graph based provenance information to
> statement provenance information (and vice versa)
> -> one can also decouple a reused statement by changing its statement
> identifier; that means, the triple of the statement are still the same
> but the relation to the original statement might now be another e.g.,
> reflected by a provenance statement e.g., <#s20> :original <#s19>
> -> statement descriptions can be typed i.e. by rdf:Statement (maybe
> obsolete now, since the new agenda propagates a deprecation of the RDF
> Reification vocabulary)
> Can such a storing be efficient for the intended use case (practical
> Named Graph implementation)?
> 2. As one can see already in the first example the application of
> property reification, the Property Reification Vocabulary [4] is
> intended for describing the definitions of such mappings on the
> vocabulary level. So, a reasoning engine can apply the two rules of the
> Property Reification Vocabulary, the shortcut relation rule[6] and the
> property reification rule[7], to infer that a binary relation particular
> and a reification class particular belonging semantically together.
> A property reification definition for the example above, would look like
> the following one:
> ex:FriendReification a prv:PropertyReification ;
> prv:shortcut :friend ;
> prv:shortcut_property :relationshipType ;
> prv:reification_class :HumanRelationship ;
> prv:subject_property :participant ;
> prv:object_property :participant .
> In this case the :friend relation would also be a symmetric relation.
> A mapping (inference) of reification class particular descriptions to
> the RDF Reification vocabulary can be done. However, I'm unsure, whether
> this is really necessary.
> Finally, I think we have to differ somehow the modelling of 'internal'
> and 'external context'. The modelling of 'internal context'
> (refinements) would still be on the same level as the usual modelling of
> binary relations. The modelling of 'external context' (i.e. provenance
> and trust) would be shifted on another level.
> Any comments, suggestions, questions and critics are very welcome.
> Cheers,
> Bob
> [1]
> http://www.dbis.informatik.uni-frankfurt.de/~tolle/Publications/2004/AISTA04.pdf
> [2]
> http://blog.dbtune.org/post/2010/12/21/Named-Graphs-and-implementations#c9094397
> [3] http://blog.dbtune.org/post/2010/12/21/Named-Graphs-and-implementations
> [4] http://purl.org/ontology/prv/core#
> [5] http://sw.deri.org/2008/07/n-quads/
> [6] http://smiy.sourceforge.net/prv/rdf/shortcut_relation_rule.n3
> [7] http://smiy.sourceforge.net/prv/rdf/property_reification_rule.n3
Received on Thursday, 15 September 2011 10:41:57 UTC

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