RE: SV: SV: SV: FW: [plcs-dex] External_class_library usage

[Peter Bergström <peter.bergstrom@eurostep.com>]

I'll look at the slides shortly, but I just have one single question immediately:

What is stopping me from having more than one context ontology? All specialized terms would be referenced from the most specialized context ontology, while the standard once would be referenced directly from the standard context rdl.

Saying:
> External_class_library http://www.dod.mil/dodaf/sv1/ and External_class
> WeaponsSystem 
Would then be unambiguous, pointing to the MoD definition, 
while:
  External_class_library http://www.projecty.org and External_class
  WeaponsSystem
Would indicate a specialization (not necessarily, but you would have to know the project y rdl to be sure).

Question is however: Is it disallowed to use several context ontologies in one data exchange, and if so, why?


Peter



-----Original Message-----
From: David Price [mailto:david.price@eurostep.com] 
Sent: den 22 december 2006 15:41
To: plcs-dex@lists.oasis-open.org
Subject: Re: SV: SV: SV: FW: [plcs-dex] External_class_library usage

Hi Peter,

I renamed the subject so make this easier to follow. I also deleted everything 
except my example and your question.

In the example from my previous email below, http://www.projecty.org and 
http://www.projectx.org are the context ontologies. The context ontology is 
the most specific, not the most generic.

Attached are slides from 2004 presentations of the approach to the Semantic 
Web and NASA/ESA PDE conferences. The MOD extension ontology is the context 
ontology in this simple example. I added the underlined/italics text today 
hoping to clarify the point.

I guess I've been assuming these ideas had made it into the minds of the PLCS 
RD developers and implementors ... clearly that was a bad assumption on my 
part. Apologies about that.

Cheers,
David

On Friday 22 December 2006 13:07, Peter Bergström wrote:
> On the context ontology, can you give me some example of how this is
> supposed to be done, from a real world use of owl? Is the context ontology
> the most specific rdl, or the most generic (i.e. the PLCS express OWL
> schema)? Is the OWL import of all rdl's wrong approach, is that what you
> say? I may come out stupid here, but I can read your statements this way,
> or the totally opposite way... Excuse me, but I'm not a native English
> (American) speaking person... I probably need the picture book examples...

No, the OWL is structured correctly wrt imports. See the attached slides. The 
issue is the use of something to specify the context within which to 
understand the RD classes that are used. I think External_class_library makes 
sense for that purpose.

>
>
> EXAMPLE
>
> Contractors cannot change the US DOD DODAF Ontology and there's a class
> there with URI http://www.dod.mil/dodaf/sv1/WeaponsSystem. In the current
> approach that's:
>
> External_class_library http://www.dod.mil/dodaf/sv1/ and External_class
> WeaponsSystem - but there's a problem lurking here.
>
> The statement that for Project X WeaponsSystem's a subclass of Product but
> for Project Y WeaponsSystem's a subclass of System_breakdown, but not
> Product, can't be defined in http://www.dod.mil/dodaf/sv1/ or anything it
> imports, it's specified in statements defined in the 
> http://www.projectx.org and http://www.projecty.org ontologies which import
> it and PLCS. So the semantics of the use of
> http://www.dod.mil/dodaf/sv1/WeaponsSystem is unknown unless you know the
> exchange is in the context of the Project X or Project Y ontology. My point
> is that conceptually this is true for every class - even those specified in
> the standard PLCS RD because you don't know if subclasses of them have been
> defined so that the use of the superclass in the PLCS RD is not allowed.
> Specifying one instance of External_class_library that's the Project X
> ontology and using External_class.id as I've suggested solves this problem.
>

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