Re: why I don't like named graph IRIs in the DATASET proposal

On Fri, 2011-09-30 at 12:02 +0200, Richard Cyganiak wrote:
> 
> > (imagine for example a owl:sameAs statement between two graphs IRI
> in a
> > SPARQL engine supporting OWL inference; what would that mean?)
> 
> owl:sameAs means that two terms denote the same resource. As written
> in the ED, use of those terms as graph names is entirely orthogonal to
> that.
> 
> I think that's a good thing. Named graphs are key to trust and
> provenance. Trust and provenance must happen at a lower level in the
> stack, before reasoning and inference kick in. W3C's version of the
> layer cake, where trust sits above reasoning, cannot work. The moment
> you reason with OWL over untrusted data, you [have problems].

I don't think we need to throw out reasoning on the fourth column.  As
long as we're careful about what it means -- eg: it denotes an IR which
may give you a Graph -- I think people are free to layer inference and
trust/provenance reasoning in various ways.  

Let's say you are using three Web data sources, S1, S2, and S3.  S1 and
S2 give just triples.  S3 is an ontology (perhaps a RIF document); we
don't really care if it's triples.   What's the problem with merging the
triples, doing the inference, and using the result, knowing it is no
more trustworthy than the least of S1, S2, and S3?   Specifically, the
provenance of your output involves the provenance of S1, S2, S3, and the
reasoning steps you took.

In detailing those reasoning steps, I think the identifiers for S1, S2,
and S3 will be useful.   

Perhaps your point is that if the reasoning on the data from S1, S2, and
S3 starts to do things with the identifiers for S1, S2, and S3, like say
S1=S2, then, yes, things get very tricky.   Self-reference.  Danger.
But for a later-stage provenance system to reason about S1, S2, and S3
is fine, I think.

     -- Sandro

Received on Friday, 30 September 2011 19:11:48 UTC