Re: dependency analysis of OWL axioms

On Sat, Nov 15, 2014 at 10:31 PM, Obrst, Leo J. <lobrst@mitre.org> wrote:
> No, I would not necessarily translate an OWL ontology to an RDF graph for these purposes, but to another graph representation, perhaps, for graph dependency analysis.

Then why are we talking about the OWL 2 RDF mapping at all? Remember
that I asked in the very beginning "In what precisely sense can they
be
represented as graphs?" to which you replied with "I understand that
all OWL ontologies can be represented as graphs, by definition into
RDF graphs". If you have another graph representation in mind, then I
go back to my point that it's unclear if your representation can
faithfully represent arbitrarily complex OWL axioms.

>Also, just to be clear, I would say that the so-called "inferred model" of the ontology, i.e., materializing from the base model to the model extended with explicit >subsumption, equivalence, etc., relations is probably the way to go.

This is may be useful or completely useless depending on what kind of
dependency we're talking about. The topic starter gave no indication
whatsoever that she's interested in inferences. I'm at a loss why
you're now suggesting inferred model.

>
> I understand that the semantics of the OWL ontology is not preserved by a simple rendition into RDF. In OWL 1, we used to talk about "dark triples", i.e., semantically uninterpretable triples.

Without more details to make it precise, this is a wrong understanding.

Please see http://www.w3.org/TR/owl2-rdf-based-semantics/, especially
Appendix 7.

>
> What I was trying to understand was why you thought that an OWL ontology could not be represented as a graph (not that it had to be represented as an RDF graph).

I did not say "cannot". Representation of an OWL ontology as a graph
is a not a goal but a tool to achieve some goal. And often a wrong
tool. But unless you specify what graph representation you have in
mind, we're both wasting our time here.

Cheers,
Pavel

>
> Thanks,
> Leo
>
>>-----Original Message-----
>>From: Pavel Klinov [mailto:pavel.klinov@uni-ulm.de]
>>Sent: Saturday, November 15, 2014 4:18 PM
>>To: Obrst, Leo J.
>>Cc: Pavel Klinov; Leila Bayoudhi; semantic-web@w3.org
>>Subject: Re: dependency analysis of OWL axioms
>>
>>On Sat, Nov 15, 2014 at 9:52 PM, Obrst, Leo J. <lobrst@mitre.org> wrote:
>>> Sure, but I do think that is generally very useful, even if it is syntactic.
>>
>>First, no, it's not just syntactic; there's semantic compatibility
>>between OWL and RDF, too.
>>
>>Second, it's useful but typically for some specific purposes, like
>>exchanging OWL documents in RDF or storing OWL ontologies in RDF (e.g.
>>in triple stores).
>>
>>However, when it comes to performing some sort of analysis on an OWL
>>ontology, such as "what depends on the given axiom", then it is
>>usually wrong to convert the ontology into RDF and analyse the
>>resulting RDF graph. You lose the structure of the ontology as a
>>logical theory and end up with a set of triples, from which it's not
>>even easy to recover original axioms. Even parsing of RDF back into
>>OWL isn't all that straightforward, let alone more complicate
>>analyses.
>>
>>>
>>> Or are you meaning that because first-order logic is semi-decidable it is not
>>useful to represent axioms and theorems as graphs? I.e., ultimately, that a
>>graph-dependency analysis of an ontology is not useful?
>>
>>Hm, I fail to see how the first question is even relevant to the
>>discussion. Re: the second, I think one should first understand what's
>>meant by "dependency" and only then suggest methods. And if by
>>"graph-dependency analysis of an ontology" you mean "convert it to RDF
>>and analyse", then I do think it is wrong.
>>
>>Pavel
>>
>>>
>>> Thanks,
>>> Leo
>>>
>>>>-----Original Message-----
>>>>From: Pavel Klinov [mailto:pavel.klinov@uni-ulm.de]
>>>>Sent: Saturday, November 15, 2014 3:17 PM
>>>>To: Obrst, Leo J.
>>>>Cc: Pavel Klinov; Leila Bayoudhi; semantic-web@w3.org
>>>>Subject: Re: dependency analysis of OWL axioms
>>>>
>>>>On Sat, Nov 15, 2014 at 9:01 PM, Obrst, Leo J. <lobrst@mitre.org> wrote:
>>>>> Pavel,
>>>>>
>>>>> How is a GCI not representable as a graph? I understand that all OWL
>>>>ontologies can be represented as graphs, by definition into RDF graphs. Do
>>you
>>>>mean something else?
>>>>
>>>>In you read my first reply to you carefully, you will see that I did
>>>>acknowledge it:
>>>>
>>>>"Of course, one can invoke the OWL2RDF mapping and take the resulting
>>>>set of triples as a (kind of) graph, but I doubt it can be generally
>>>>useful."
>>>>
>>>>But what are you going to do with that graph then?
>>>>
>>>>Cheers,
>>>>Pavel
>>>>
>>>>>
>>>>> Thanks,
>>>>> Leo
>>>>>
>>>>>>-----Original Message-----
>>>>>>From: Pavel Klinov [mailto:pavel.klinov@uni-ulm.de]
>>>>>>Sent: Saturday, November 15, 2014 5:08 AM
>>>>>>To: Obrst, Leo J.
>>>>>>Cc: Pavel Klinov; Leila Bayoudhi; semantic-web@w3.org
>>>>>>Subject: Re: dependency analysis of OWL axioms
>>>>>>
>>>>>>On Fri, Nov 14, 2014 at 10:51 PM, Obrst, Leo J. <lobrst@mitre.org> wrote:
>>>>>>> Thanks, Pavel.
>>>>>>>
>>>>>>> My question is about your comment:
>>>>>>>
>>>>>>> "OWL is quite a rich language and one can write very complex axioms
>>>>which
>>>>>>don't look anything graph-like."
>>>>>>>
>>>>>>> I'd like to know your thoughts on this.
>>>>>>
>>>>>>For example, in OWL 2 DL one can take all (class) axioms and re-write
>>>>>>all that into a single long GCI.
>>>>>>
>>>>>>Cheers,
>>>>>>Pavel
>>>>>>
>>>>>>>
>>>>>>> Thanks!
>>>>>>> Leo
>>>>>>>
>>>>>>>>-----Original Message-----
>>>>>>>>From: Pavel Klinov [mailto:pavel.klinov@uni-ulm.de]
>>>>>>>>Sent: Friday, November 14, 2014 3:59 PM
>>>>>>>>To: Obrst, Leo J.
>>>>>>>>Cc: Leila Bayoudhi; semantic-web@w3.org
>>>>>>>>Subject: Re: dependency analysis of OWL axioms
>>>>>>>>
>>>>>>>>On Fri, Nov 14, 2014 at 5:42 PM, Obrst, Leo J. <lobrst@mitre.org> wrote:
>>>>>>>>> We had proposed this a number of years ago, but never had time to
>>go
>>>>>>down
>>>>>>>>that path. More towards trying to infer "integrity constraints"
>>dynamically
>>>>>>(yes,
>>>>>>>>OWL is Open World; integrity constraints are Closed World). Finding the
>>>>>>ripple
>>>>>>>>effect of deleting, adding, moving graph nodes that kind of corresponds
>>to
>>>>>>>>"referential integrity" (i.e., structural) in the database world. Since all
>>OWL
>>>>>>>>ontologies (the axioms) can be represented as graphs, it should be
>>doable.
>>>>>>How
>>>>>>>>efficiently, I don't know.
>>>>>>>>>
>>>>>>>>
>>>>>>>>I'd be very, very cautious with statements like "OWL axioms can be
>>>>>>>>represented as graphs". In what precisely sense can they be
>>>>>>>>represented as graphs? OWL is quite a rich language and one can write
>>>>>>>>very complex axioms which don't look anything graph-like. Of course,
>>>>>>>>one can invoke the OWL2RDF mapping and take the resulting set of
>>>>>>>>triples as a (kind of) graph, but I doubt it can be generally useful.
>>>>>>>>
>>>>>>>>I can imagine that for some very specific tasks, like decomposition
>>>>>>>>(as in [1]), a graph-based representation of OWL axioms can be
>>>>>>>>helpful. But such use cases (and the corresponding representations)
>>>>>>>>tend to be pretty specific rather than generic.
>>>>>>>>
>>>>>>>>Cheers,
>>>>>>>>Pavel
>>>>>>>>
>>>>>>>>[1] Francisco Martín-Recuerda, Dirk Walther: Axiom Dependency
>>>>>>>>Hypergraphs for Fast Atomic Decomposition of Ontologies. Description
>>>>>>>>Logics 2014: 299-310
>>>>>>>>
>>>>>>>>>
>>>>>>>>> Thanks,
>>>>>>>>> Leo
>>>>>>>>>
>>>>>>>>>>-----Original Message-----
>>>>>>>>>>From: Leila Bayoudhi [mailto:bayoudhileila@yahoo.fr]
>>>>>>>>>>Sent: Friday, November 14, 2014 6:36 AM
>>>>>>>>>>To: semantic-web@w3.org
>>>>>>>>>>Subject: dependency analysis of OWL axioms
>>>>>>>>>>
>>>>>>>>>>Hello
>>>>>>>>>>I want to know if there is a tool or an approach realizing dependency
>>>>>>>>annalysis
>>>>>>>>>>of OWL 2 axioms.
>>>>>>>>>>Example:
>>>>>>>>>>by removing a subClassOf axioms , I want to know affected ones in
>>the
>>>>>>>>>>ontology.
>>>>>>>>>>Or, can I do it manually by recognizing different types of axioms and
>>>>>>>>expecting
>>>>>>>>>>relations between them.
>>>>>>>>>>Thank you for answering me.
>>>>>>>>>>--398296598-735493131-1415964971=3759
>>>>>>>>>>Content-Type: text/html; charset=f-8
>>>>>>>>>>Content-Transfer-Encoding: quoted-printable
>>>>>>>>>>
>>>>>>>>>><html><body><div style="color:#000; background-color:#fff; font-
>>>>>>>>>>family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida
>>Grande,
>>>>>>sans-
>>>>>>>>>>serif;font-size:16px"><div>Hello</div><div>I want to know if there is
>>a
>>>>>>tool
>>>>>>>>or
>>>>>>>>>>an approach realizing dependency annalysis of OWL 2
>>>>>>>>>>axioms.</div><div>Example:&nbsp;</div><div>by removing a
>>>>subClassOf
>>>>>>>>>>axioms , I want to know affected ones in the ontology.</div><div>Or,
>>>>can I
>>>>>>>>do it
>>>>>>>>>>manually by recognizing different types of axioms and expecting
>>>>relations
>>>>>>>>>>between them.</div><div>Thank you for answering
>>>>>>>>>>me.</div></div></body></html>
>>>>>>>>>>--398296598-735493131-1415964971=3759--
>>>>>>>>>>
>>>>>>>>>

Received on Saturday, 15 November 2014 21:54:10 UTC