|From:||Leo Obrst <lobrst@xxxxxxxxx>|
|Date:||Fri, 07 Mar 2003 09:50:42 -0500|
FYI: Mike, this forum is now named ontolog-forum@xxxxxxxx -- per your message
and my reply below. I thought there was an alias, but I haven't seen it
-------- Original Message --------
We've recently been discussing a variant of this question internally (in MITRE) across two communities, the database and the ontology folks. I.e., data modeling vs. ontology engineering. I think our point of departure was the SIGMOD paper from last year:
Data Modelling versus Ontology Engineering. P. Spyns, R. Meersman, M. Jarrar, Special Section on Semantic Web and Data Management, V. 32:4, December, 2002. http://www.acm.org/sigmod/record/issues/0212/SPECIAL/2.Meersman.pdf.
Note the above requires a login account.
I think the short answer is that database schemas and XML Schema are a way of structuring data/document collections for some generally local purpose, e.g., to satisfy an application (or set of applications) or, in the case of XML Schema, for some generally local exchange of documents/messages. So, in general, schemas are focused on structure rather than the meaning of constructs that define that structure. And ontologies address a more "global" view, in terms of real world semantics.
*However, we all know that structure is the mother of meaning too, that in fact no semantics is possible without it, and that the formal objects on the "semantics" side to which the syntax/structures map (in model-theoretic semantics via an interpretation function) and which we take to "stand in" for the real/possible world entities whose semantics we want to capture, are themselves structured (probably because we want those objects to have certain formal properties, ordering relationships, etc.)
That said, maybe the shortest answer is: A constraint in an XML Schema is a constraint on the structure or form of a document, not on the meaning of a real world object as in an ontology.
"Uschold, Michael F" wrote:
It is not usual for someone to show me an XML shema and say, "Hey, what do you think of my ontology?", or: "Gee, we are using an ontology now, but everyone's using XML, so maybe we should use an XML Schema instead?". Indeed, some people have the impresson that XML Schema and ontologies** are similar animals and one can use one or the other for a given problem.--
Dr. Leo Obrst The MITRE Corporation
mailto:lobrst@xxxxxxxxx Intelligent Information Management/Exploitation
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