Re: RDF named graph use case and requirement

Hi Graham,
I'm not sure if I got your idea correctly, but in my understanding of the
model I was assuming that
Pra and Prb *are different named graphs* (provenance containers ;) ) wich
happen to contain the
same triples. That is, Pra and Prb have different URIs, even if at a certain
moment of time the
graphs have the same content. Since Pra and Prb have different identifiers,
we can assert provenance statements
using them as subject as if they were just regular resources. I don't see
the problem here :(

Best,
Daniel

2011/9/21 Graham Klyne <GK@ninebynine.org>

> (I've also posted this summary at http://www.w3.org/2011/prov/**
> wiki/ProvenanceRDFNamedGraph#**Requirement_from_discussion_**
> with_Andy_Seaborne<http://www.w3.org/2011/prov/wiki/ProvenanceRDFNamedGraph#Requirement_from_discussion_with_Andy_Seaborne>
> )
>
> In a meeting with Andy Seaborne this morning, we discussed provenance
> requirements and RDF named graphs, in light of some options that the RDF
> group might be considering.
>
> The resulting requirement that we articulated was that for the purposes of
> provenance, we must be able to treat two "named" graphs with identical graph
> content as two distinct entities.
>
> ...
>
> The use-case is this:
>
> Suppose we have some resource R.
>
> Observer A makes a provenance assertion about R on Monday 2011-09-19, which
> is expressed as an RDF graph Pra
>
> Observer B makes a provenance assertion about R on Friday 2011-09-23,
> expressed as RDF graph Prb
>
> To express provenance about the provenance assertions, we may wish to say:
>
> Pra statedBy A; onDate "2011-09-19" .
>
> Prb statedBy B; onDate "2011-09-23" .
>
> It may be that the provenance assertions Pra and Prb have identical
> content; i.e. they are RDFG graphs containing identical triple sets.  For
> the purposes of provenance recording, it is important that even when they
> express the same graphs, Pra and Prb are distinct RDF nodes.  If Pra and Prb
> are treated as a common RDF node, one might then infer:
>
> _:something statedBy A ; onDate "2011-09-23" .
>
> which in this scenario would be false.
>
> .....
>
> A particular consequence of this is that an RDF "named graph" specification
> based on graph literals (where RDF literals are self-denoting), somewhat
> like formulae in Notation 3, would have to be used with care.  That is, if
> Pra and Prb are graph literals, then Pra = Prb, and the given
> provenance-of-provenance statements could not be expressed as suggested
> above.
>
> (This does not preclude a graph literal approach being used, but the above
> use-case might need to be constructed slightly differently.)
>
> #g
> --
>
>