Re: Semantic Web and First Order Logic
Bullard, Claude L (Len) wrote: > Is it true or false that the semantic web > limits the use of First Order Logic RDF is less expressive than FOL, yes. N3 is closer as it has things like quantifiers. OWL has 3 levels to cater for how much you want ranging from 'I could hack that together' to 'this may never be implemented fully'. This concern about decidability on the semantic web comes from description logics work. DLs are carefully designed to allow engines to be tractable and scalable when it comes to generating results; the downside is that it makes some things awkward to say and enforces constraints based on what you can expect a reasoning engine to be able to deal with, whether or not you care about reasoning engines. IMVHO,if you force content providers and developers to chow down on a DL for a length of time, they'll ask for a scripting hook. Which kind of defeats the point of using a logic to begin with. Pat Hayes has written (a very nice read) on how DLs square with the semantic web : [[[ The semantic web doesnt need all these DL guards and limitations, because it doesn't need to provide the industrial-quality guarantees of inferential performance. Using DLs as a semantic web content markup standard is a failure of imagination: it presumes that the Web is going to be something like a giant corporation, with the same requirements of predictability and provable performance. In fact (if the SW ever becomes a reality) it will be quite different from current industrial ontology practice in many ways. It will be far 'scruffier', for a start; people will use ingenious tricks to scrape partly-ill-formed content from ill-structured sources, and there is no point in trying to prevent them doing so, or tutting with disapproval. But aside from that, it will be on a scale that will completely defeat any attempt to restrict inference to manageable bounds. If one is dealing with 10|9 assertions, the difference between a polynomial complexity class and something worse is largely irrelevant. And, further, almost all of this content will be extremely simple and shallow, seen from a logical perspective. Worrying about the complexity class of the few intricate ontologies on the web is like being obsessed with the quality of the salt in a supermarket. ]]] > I realize that FOL has the undecidability > problem, but is sufficient for everyday > reasoning and is the most widely used > logic in business. I believe that would be EC logic as used in relational databases and Prolog. Otherwise the most widely used 'business logic' is whatever you can get to run in a middleware. > I realize that is controversial and is > deliberately so. I am wondering if the > semantic web is somewhat over-engineered. It's hardly engineered at all Len, that's the problem ;) Bill de hÓra -- Propylon www.propylon.com  http://www.aifb.uni-karlsruhe.de/~sst/is/WebOntologyLanguage/hayes.htm
PURCHASE STYLUS STUDIO ONLINE TODAY!
Purchasing Stylus Studio from our online shop is Easy, Secure and Value Priced!
Download The World's Best XML IDE!
Accelerate XML development with our award-winning XML IDE - Download a free trial today!
Subscribe in XML format