Re: [Dbpedia-discussion] Using DBpedia resources as skos:Concepts?

On Thu, Nov 5, 2009 at 5:48 PM, Simon Reinhardt <simon.reinhardt@koeln.de>wrote:

> Simon Spero wrote:
>
>> There are practical implications for indexing that follow from this
>> decision.  For example, the SKOS broader relationship is not transitive;
>> this is hard to understand with a document based domain of interpretation.
>>  Without transitive BT relationships, standard indexing behaviors like
>> upward posting, or assigning the most specific headings to a document are no
>> longer possible  (or rather, give different results).
>>
>
> But that's what skos:broaderTransitive is for? As a super-property of
> skos:broader it will always be inferred if you just declare a skos:broader
> relationship between two concepts, plus it's transitive. So if you want to
> find transitively broader concepts you query for skos:broaderTransitive but
> if you want directly declared relationships you just query for skos:broader.
>
> So not sure where your problem lies.
>

BroaderTransitive is not supposed to be asserted, and is not required to be
valid- “the semantics of skos:broader, [..] cannot enforce such
transitivity" (Issac and Summers 2009).

The change to the semantics of broader was made due to confusion about the
meaning of transitive relationships that  spanned different  broader
relationships that arises if the document centric model is not followed.
The example used is:

In many cases, hierarchical relations in a concept scheme can be considered
as transitive [OWL]. If ex:animals is broader than ex:mammals, which is
itself broader than ex:cats, it makes sense to assert that ex:animals is
broader than ex:cats. However, there are "dirtier" hierarchies, especially
in KOSs different from standard well-designed thesauri, where such a feature
would not be judged appropriate. Consider for instance a case where
ex2:vehicles is said to be broader than ex2:cars, which is itself asserted
to be broader than ex2:wheels. It may be problematic if "wheels" is
automatically inferred to be a narrower concept with respect to "vehicles".
(Issac and Summers 2009).

This is entirely unproblematic in KOSes, where the extensions of Concepts
are documents.

Simon
-----
Antoine Isaac and Ed Summers (2009). SKOS Primer. W3C. URL:
http://www.w3.org/TR/skos-primer