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Subject: RE: [regrep-semantic] [UDEF]
I very much agree with Evan's analysis. It is very hard to express an ontology with single tree that let along one that doesn't have typed relationships. It becomes even more difficult when one tries to take the tree cross industry and international. -----Original Message----- From: ewallace@cme.nist.gov [mailto:ewallace@cme.nist.gov] Sent: Friday, February 06, 2004 5:59 PM To: carlmattocks@checkmi.com Cc: regrep-semantic@lists.oasis-open.org Subject: Re: [regrep-semantic] [UDEF] "Carl Mattocks" <carlmattocks@checkmi.com> wrote: >This is interesting. I want to now more.. > >Zach: > >Please expand on the notion of 'UDEF semantic identifiers'. > >Evan: > >Please elaborate on 'lattices of these relationships '. > I meant networks rather than strict trees. A simple example network is a class with multiple inheritance. There are also horizontal relationships like synonyms and properties. Think about a design model of a racecar which describes different component systems. All of these components have a partOf relation to the car. Something like a transmission often plays at least two different roles in a hierarchy of component systems in a racecar. It is partOf the drivetrain and may be partOf the load bearing structural system. Twisting all these properties and relationships into a strict hierarchy leads to awkward models such as the UDEF Object tree. I didn't mean to imply that supporting lattices was unusual for modeling languages. It isn't. I was arguing that such expressiveness is necessary for useful semantic models. >Everyone : > >Please consider if the Semantic Web could leverage "concepts ... denoted >by the paths from these nodes to the root rather than the node itself" To a certain extent they already do. I was trying to simplify a finer distinction. The path back to the root through subtype relations in an RDFS or OWL model of course has implications on a class and instances (individuals) of that class. Just the implications you would expect if you have programmed in an Object Orient programming language. If Racecar is a subtypeOf Car is a subtypeOf Vehicle, then any Racecar instance is also a Car and a Vehicle instance and inherits the characteristics of those supertypes. By constrast, the relations in the UDEF Object tree do not have any explicitly defined implications. It's only when you have followed the path that you might be able to infer what the relations might have been along each connection in the path. This makes the tree hard to navigate when looking for a specific concept. It also can lead to related or similar concepts being located quite far apart in the tree. -Evan
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