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Re: [ontolog-forum] Interpreting OWL

To: "'[ontolog-forum] '" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: "Matthew West" <dr.matthew.west@xxxxxxxxx>
Date: Sun, 17 Oct 2010 13:52:03 +0100
Message-id: <4cbaf17a.10d0e30a.3e9d.1599@xxxxxxxxxxxxx>

Dear Sean,


The statement was made that anything that could be written in EXPRESS could be written in OWL.

MW: I am not completely certain of that. Almost always different languages have different capabilities. However, it is probably true that most of what can be usefully written in EXPRESS could be written in OWL.

However, some of the constructs in EXPRESS, particularly those concerning the cardinality and structure of relationships are not directly obviously expressible in OWL, such as the distinction between a bag and a set. However, it should be possible to create a first order interpretation of OWL such that an EXPRESS relationship is a subtype of 'thing', and the relationship constraints are then OWL properties. EXPRESS Entity and Type also become subtypes of 'thing'

MW: Entity at least should probably be a subtype of class rather than thing. However, I think the real mistake in what you are doing here is trying to place one language in another. My experience has been that doing this produces very clunky results, and that a much better approach is to look at the new language, and what you were originally trying to say (before you put it in EXPRESS) and find the best way to say it in the new language. You are likely to find both things that can be said in more elegant ways, and things that can be said in less elegant ways, as well as some things you can now say that you could not say before, and some things you cannot now say.

This then allows one to construct a second order interpretation by suptyping Entity, Relationship and Type as STEP generic entities, such as Product, Version, View, Property, Property-Representation, Representation-Presentation etc. That is, EXPRESS entities provide an upper level ontology for STEP in OWL.

MW: Well this is some of the stuff that is what you really wanted to say. I would start here and look at how best to put these into OWL directly. However, I would take the opportunity to clean some things up along the way.

One can then create a third order interpretation, as is done in the STEP Application Protocols, in which the STEP generic entities are interpreted in the context of a business process, so that Product is either a product (AP 203) a part (AP 214) or a technical data package (AP 232).

MW: The main problem here is the interpretation process, which means that some STEP entities in the integrated resources are essentially treated as constructs without a particular meaning attached to them. Again, I would go back to what you really wanted to say, and eliminate any objects where there is interpretation that is not a subtyping – at the very least.

Two questions arise. Firstly, one could also describe other modelling languages such as UML and IDEF1X as first order interpretations of OWL (in the sense above) (and even of OWL itself). Could one then compare the expressive power of such formalisation by creating a lattice of modelling languages? (This would also expose ambiguities in the languages).


Secondly, would the second and third order interpretations be compatible with anybody else's use of OWL?

MW: Why would anyone’s use of OWL be compatible with anyone else’s?




Matthew West                           

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For example, whether a particular (EXPRESS) property is a property of a product is contingent on the Version (an implied temporal commitment) and the View.

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