Hi Vladimir,
On 11/6/2013 12:11 μμ, Vladimir Alexiev wrote:
The reason is simple: RDFS does not contain owl:same_as. We (you)
can make an owl version that solves the problem.
owl:sameAs is a different construct from owl:equivalentClass.
You don't have to use owl:equivalentClass though. You can stay in the
rdfs vocabulary by using rdfs:subClassOf in both directions, as I
wrote previously.
See http://www.w3.org/TR/owl-ref/#equivalentClass-def : If we wanted
to "upgrade" an axiom of the form "A subClassOf B" to "A
equivalentClass B" (meaning that the class extension of A is not just
any subset, but in fact the same set as the class extension of B), we
could add a second subClassOf axiom of the form (B subClassOf A),
which by definition makes the two class extensions equivalent (and
thus has the same meaning as "A equivalentClass B"). Such subClassOf
"cycles" are explicitly allowed.
The naming is more political. Some class names should look more
FRBRish.
OK, thank you, we'll do so.
The spirit of the sem web is to reuse existing ontologies as much as
possible. CRM doesn't do that, e.g. it doesn't relate to previously
defined common classes for places, times, events, concepts, etc.
Well, Vladimir, that's a strong statement! Where is the spirit of the
Semantic Web that never referred to a CRM class, even though the CRM
exists since 1996, and is an ISO standard since 2006? The CRM is much
older than most of the Semantic Web ontologies.
For instance,
dcterms:Location
is defined as "A spatial region or named place. For Darwin Core, a set
of terms describing a place, whether named or not."
How can we refer to so poorly defined concept? Why did they not reuse
the CRM? Why did Europeana redefine all CRM Concepts, after a decision
was taken to reuse them in a public meeting?
We rely on Harmonization, and not blindly import poorly defined
concepts. Semantic interoperability is only achieved if concepts are
sufficiently precise.
But
I can live with that since CRM is a self-contained intellectual
effort,
I am relieved.
Best,
martin
and such semantic relations (subClass and equivalentClass)
have wide-ranging consequences that are very nontrivial to analyze.
AFAIK, Simon Reinhardt is the first to attempt this, see
http://lists.ics.forth.gr/pipermail/crm-sig/2009-September/001393.html
However, FRBRoo is explicitly an extension of CRM. For FRBRoo not to
"clean up" its classes, and not to use CRM classes directly where
appropriate, seems like intellectual sloppiness to me. And disregard
for the practical implementers of these ontologies.
Steve> this is a joint project between 2 communities IFLA and CRM
SIG.
Yes, and these groups work closely together, have identified the
equivalent classes, and I see no impediment to merge the classes
now.
Why you materialize all superclass links is not clear to me. No
one queries "all persistent items" or so. Not all triple stores do
that.
Could you give an example of *any* CRM system that does *any* useful
reasoning but doesn't materialize the inferences mandated by CRM?
Note: CLAROS doesn't have any reasoning, as you can check at
http://data.clarosnet.org/sparql/ by comparing this query
SELECT * WHERE { ?s a crm:E53_Place; crm:P87_is_identified_by ?o }
LIMIT 50
to this one
SELECT * WHERE { ?s a crm:E53_Place; crm:P1_is_identified_by ?o }
LIMIT 50
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