- From: Dieter Fensel <dieter@cs.vu.nl>
- Date: Fri, 04 Jan 2002 02:41:26 +0100
- To: www-webont-wg@w3.org
- Cc: Dieter Fensel <dieter@cs.vu.nl>
How to layer the semantic web properly? We had recently a large amount of discussions on the right layering of OWL and RDF. This is not really surprisingly because it touches a key issue of the semantic web. How to understand the layering of the various elements that Tim put in his visionary slide on top of each other (see [1]). I would like to provide the following intuitions: 1. This layering cannot be interpreted in model-theoretic terms. That is, we cannot expect that each set of inferences at a higher level is a super set of all inferences at a lower level. Each level will have its specific style on how to draw inferences. Therefore: - we should not be surprised if the rule language will choose some kind of minimal model semantics that differs from our OWL semantics. - we should not worry too much that a Pat Hayes RDF agent draws some conclusions an OWL agent would never dare to take. Instead of viewing this as a bug we should view it as a nice feature that provides the world with different reasoning styles. 2. I would strongly recommend to keep the layers syntactically as close as possible. Even if a Pat Hayes aware RDF agent draws some strange conclusions in the average we will win a lot if an RDF agent can process the syntax of OWL statements and if it draws conclusions which are reasonable for its level and even right in the average for an OWL agent. 3. It is highly desirable that OWL has a sound model theory. This can easily be achieved. Only if one uses RDF as a syntax AND as a semantics (i.e., if somebody makes the mistake to define the OWL semantics as an extension of the Pat Hayes RDF semantics) then he runs into problems. My personal conclusion: Lets define a simple semantics of OWL without reference to the model theories of other working groups. Or spoken as a sociologist: I see some changes that we agree on syntax between different working groups but we will run in endless war or non-compatibility if we try to agree on the basis of model theory between different working groups. 4. The question whether to base OWL syntactically on XML or RDF is a question of high strategic impact. Such a question can neither be decided on the background of problems in expressing DAML+OIL lists in RDF nor based on problems in monotonically extending Pat Hayes RDF model theory. There need to be much more serious arguments to justify such a schism of the semantic web. Dieter ---------------------------------------------------------------- Dieter Fensel Division of Mathematics & Computer Science, Vrije Universiteit Amsterdam, De Boelelaan 1081a, 1081 HV Amsterdam, NL The Netherlands Tel. (mobil): +31-(0)6-51850619, Fax and Answering machine: +31-(0)84-872 27 22 Email: dieter@cs.vu.nl ICQ #132755538 http://www.google.com/search?q=dieter or http://www.fensel.com Privat: Liendenhof 64, NL-1108 HB Amsterdam, The Netherlands. Tel.: +31-(0)20-365 52 60. ---------------------------------------------------------------- The information transmitted is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon, this information by persons or entities other than the intended recipient is prohibited. If you received this in error, please contact the sender and delete the material from any computer.
Received on Thursday, 3 January 2002 20:43:32 UTC