Re: OWL Full reasoning

On 8/18/05, Hans Teijgeler <hans.teijgeler@quicknet.nl> wrote:

> First question - have you determined the inferences you are looking 
> 
> for are actually available through OWL Full semantics? 
> 
> [HT] To be brutally honest: I don't have a clue. Where can I read about that
> in non-logician terminology? 

Good question. The best I can think of is the OWL Guide [1], but
that's still not entirely friendly.

> My guess is that whether or not this is the case then the reasoning is
> likely 
> 
> possible with existing tools using a subset of OWL Full + rules  (e.g. 
> 
> using  cwm, Euler or Pychinko). 
> 
> [HT] I am not one of the OWLites, and keep having problems to find what to
> learn and what to do. I tried every OWL Validator that I could find on the
> W3C site, but the only thing these do is telling me that they have a parsing
> problem, without telling me why that is. You guys still have a LOT to do in
> order to make OWL a bit more userfriendly and accessible for the lesser
> initiated. I'll try the three you mention (if I can find them). 

The only online validator I'd personally recommend at this point in
time is the W3C RDF validator [2], which will tell you if your syntax
is ok but little more (except a big diagram ;-)

> Next questions - are you tied to this representation? Cannot the same 
> 
> information be refactored to be OWL DL? 
> 
> [HT] In our little world that is being debated. I am against it, because
> that would mean denormalization, and we would lose too much of the
> expressivity of ISO 15926, and lifetime stability (see below). 

I'm not familiar with ISO 15926 so can't really comment, except to say
that more expressive languages are harder to reason across. It could
be the case that sound (no wrong inferences are drawn) and complete
(all the correct inferences are drawn) reasoning isn't possible over
the ISO 15926 model using a general-purpose logic. Which would mean
resigning yourself to either an app-specific reasoning engine or using
a less expressive subset of the language (like OWL DL vs. OWL Full).

> For example, you have "2" 150/300#RF Flanged Connection" as subClassOf 
> 
> "ClassOfDirectConnection", yet an instance of "Valid Connection per 
> 
> ANSI B16.5". Might it not be reasonable to make it a subClass of the 
> 
> latter too? 
> 
> [HT] Not if I want to stay in compliance with ISO 15926. A
> ClassOfDirectConnection may only be used for things like "electrical
> connection", "hydraulic connection", etc. In case you want to express things
> like "flexible connection" then you have to use a metametaclass (that
> ClassOfClass) (the data model is close to 5th Normal Form). 

The naming clash may be confusing things here, e.g. owl:Class is the
ClassOfClass in OWL, but almost certainly doesn't mean the same thing
as ClassOfClass in ISO 15926. So rdfs:subClassOf  *might* adequately
express the "Valid Connection per  ANSI B16.5" relation in the ISO
15926 model. (I don't know ;-)

> [HT]  Any logician in the room? 

Corridor? Bar? Powder room?
 
> [HT] In the process industries (and in other industries as well) there is a
> need to be able to: 

[snip - data integration/sharing]

> This means that the data model must be very solid, generic, and rigorous,
> and that the medium (here OWL) may (and will) disappear before the end of
> that lifetime. The data model has 201 entity data types only, and is
> data-driven by means of what we call a Reference Data Library (the "Part 4"
> balloons are in that library). Right now we have some 20,000 classes, and
> when we are ready in 20 years or so we may have reached 100,000. 
> 
> We worked on that data model since the late eighties (I joined in 1992), and
> it became IS (ISO International Standard) in December 2003. 
> 
> Since 2000 we worked on an implementation standard and based it on XML
> Schema, for lack of something better at that time. I want to make the move
> to OWL, because for the most it fits hand-in-glove.But I tell you, it ain't
> easy for a data modeller to grasp the intricacies of RDF and OWL. 
> 
> I'll get off my soap box…. 

I'll get on mine ;-)
XML validation will give you syntax checking, but your example
suggests you want more than that. Using RDF will give a shareable data
model (in the sense that it could potentially be shareable across
industries/domains, not just between companies in the same domain).
What you'd have with the XML Schema representation is a shareable
syntax, but the data model would remain dependent on your current
modeling language. Which is a good question - what is your current
modelling language? How are the logical relations expressed? To what
extent can you do inference across it?

You mentioned 5th normal form - I have a habit of forgetting the
normal forms seconds after I've looked them up, but I think this
probably bodes well. The RDF model is relational (the relations being
the predicates/properties), and is fairly normalised when viewed
alongside the usual relational model (lotsa little tables, URIs/bnode
IDs as keys)

RDF is very expressive, and I think the example you've provided
suggests it can express the ISO 15926 data. But whether OWL can
provide the full set of constraints required is another matter. But
this would only be essential if you wanted OWL to provide
sound/complete consistency checking.

> [HT] I figured that we will need to write code ourselves indeed. That still
> leaves me with the question: What's the use of OWL? 

Provides a common data model with a useful level of logical
constraint. In a case like this you may need stuff outside of RDF/OWL,
but at least there's a good foundation.

> One final question - do you happen to have this available as RDF/XML 
> 
> or other serialization? 
> 
> [HT] You can find the Ontology for Data Mode :under: 
> 
> http://www.infowebml.ws/links/ontology-for-data-model.rdf 

Thanks.

> I will write OWL code for the problem I painted, and send it later (mind
> you, until now I haven't found an OWL IDE, so I write the whole stuff by
> hand, check it for XML well-formedness with XMLSpy (a leftover from my XML
> Schema days), validate RDF with the W3C RDF Validation Service, and then I
> get stuck. The Pellet guys, for example, want me to be a member (of what
> they didn't tell on their screen), and just tell me that their moderator
> will look at the error report that I filed. He/she is probably on vacation….

Sounds like it's a job for Protege [3]. It's a powerful IDE which
includes OWL support and a variety of reasoners. One caveat - in my
experience it's a little flaky at times (crashing on certain imports
for me). I don't know, if you have your data model fully expressed in
another language (entity-relation or something) then there may be a
direct way of translating across - Protege supports allsorts through
plugins.

Cheers,
Danny.

[1] http://www.w3.org/TR/owl-guide/
[2] http://www.w3.org/RDF/Validator/
[3] http://protege.stanford.edu/

-- 

http://dannyayers.com

Received on Friday, 19 August 2005 10:17:46 UTC