RE: [SKOS, SPARQL, ALL] Closure and SPARQL

>Hi all,
>
>I realize I should never have mentioned the 
>domain-range, and never should have used 
>"inferred". I understand why Gary, and I imagine 
>a lot of other people, got very confused when I 
>brought this up. This is beyond the scope of the 
>query language since "new" information is 
>"added" to the graph and would require a 
>reasoner or similar mechanism. This was never my 
>intention.
>
>All I wanted to point out was transitive 
>closure. And has been noted by E.Franconi: " you 
>need a full fledged "graph" query language, 
>while I guess that SPARQLl suffers of a mixed 
>origin: a bit of SQL/relational data model and a 
>bit of graph data model."
>
>Thatıs all. RDF is a graph, it has native transitive properties.

That phrase does not make sense to me. Can you 
please explain what you mean by 'native 
transitive'?

RDF uses a graph *syntax*, but that is merely a 
syntactic convention. Nothing follows from this 
about transitivity or otherwise of the relations 
described by an RDF graph.

>Being able to express in query that only the 
>direct nodes should be taken into account, or 
>that the transitive nature of the properties has 
>to be taken into account is a logical step.

What is a 'direct node'?

RDF does not require *any* properties to be 
transitive. RDFS requires rdfs:subClassOf and 
rdfs:subPropertyOf to be transitive, but nothing 
else.  Are you referring to queries that assume 
RDFS completion of the query graph, i.e. that it 
is closed under RDFS entailment?

>  No more, no less.
>The complexity of introducing this: minimal. I 
>only mentioned it because it has some 
>implications, it won't implement itself. I just 
>got the impression that there was a concern that 
>implementing this would be far to complex. It 
>isn't.
>Hierarchical queries do something similar, and 
>their implementations and syntax vary.
>And thatıs exactly what I meant by 
>"non-standard": some implementations will add 
>their own keywords to SPARQL to add this 
>feature. Others will opt to define the indirect 
>variant of a transitive property, like 
>ns1:indirectSubclassOf for rdfs:subClassOf, or 
>as has already been suggested, 
>skos:inNarrowerClosure for skos:narrower. 
>Namespaces will vary, keywords will vary, 
>implementations will vary, and interoperability 
>between systems will be lost. It is far from 
>unwarranted.
>
>The /*+RULE*/ example was not a great one, but 
>the comparison to hierarchical queries still 
>holds: For a standard database there was already 
>a need to create hierarchical queries. Rdf has a 
>hierarchy in classes and properties because the 
>property is transitive.

RDF makes no transitivity assumptions at all. 
RDFS makes it for subClass and subProperty. Are 
you talking about RDF or RDFS?

Pat Hayes


-- 
---------------------------------------------------------------------
IHMC		(850)434 8903 or (650)494 3973   home
40 South Alcaniz St.	(850)202 4416   office
Pensacola			(850)202 4440   fax
FL 32502			(850)291 0667    cell
phayesAT-SIGNihmc.us       http://www.ihmc.us/users/phayes

Received on Monday, 12 December 2005 17:58:41 UTC