On Nov 28, 2013, at 1:24 PM, John McClure <jmcclure@xxxxxxxxxxxxxx> wrote: (01)
> Hi Pat
>>> <snip/>
>>> Where can I find more information about the fourth part of the quad. I'm
>>> assuming that's to point to a provenance object defined by the PROV
>>> standard
>> That assumption illustrates the basic problem: there is no way to
>standardize the multifarous potential uses for the fourth quad field. To my
>knowledge it has been used as a graph label, as an extra relational parameter,
>to encode a time reference, to indicate a source (but not using PROV: that
>usage pre-dates PROV by several years, maybe a decade), and simply as an
>indexing mechanism inside a quad store. I am sure that there are others. So,
>implementations use it (and some even use quints) but its not part of any
>normative RDF standard because it doesn't have a coherent semantics.
> I'm wondering if a semantic is even needed for a 'quad field' that
> points to PROV data -- provenance appears to me a different level of
> discourse, (02)
Not in the RDF world. the PROV standard is rife with RDF being used to describe
provenance. (03)
> actually much like xml:lang, which (merely?) happens to be a
> field in a DC provenance description.... it seems to me that if items
> like xml:lang are /not captured/ within a PROV/DC then yes, the
> alternative is /major chaos/ as quads give way to quints whic give way
> to ... these higher order "ints" can be performance-savvy for database
> operations, but questionable from an interchange perspective.
>
> A standardized PROV/DC addition to rdf:Statement seems reasonable to me,
> perhaps best not as a property value but in some other way. A somewhat
> common use for a quad-field I've seen is to name a/the DAG in which the
> triple exists, (04)
DAG? Why would an RDF graph not be cyclic? (05)
> but this could be as easily the content of a "publisher"
> or "subject" field within a provenance description. (06)
The basic issue is, how do you make an IRI refer to an RDF graph? It would seem
like that is what an RDF dataset is for, but that is not what the specs say.
Without some such 'baptism' of graphs, using RDF to describe provenance of
graphs is dead on arrival. (07)
Pat (08)
>
> I need to find time to dig into the PROV spec, maybe this is
> covered..Thanks/jmc
>
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> (09)
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