From: Dan Connolly (connolly@w3.org)
Date: 09/07/01
pat hayes wrote: > > >Richard Fikes wrote: > > > > > > As I mentioned yesterday in the telecon, a student of mine, Yulin Li, > > > and I have designed a simple language for querying DAML+OIL knowledge > > > bases. The language is specified as a DAML+OIL ontology so that both > > > queries and the results obtained from asking a query are represented in > > > DAML+OIL. > > > >I appreciate the effort of specifying the language as a DAML+OIL > >ontology. > > Well, I wonder what the point of this effort was, and would like to > raise this as an issue for discussion. Very well... but the discussion isn't really about the query language proposal, so I've edited the subject header field... > It seems to me to be: > > (a) completely pointless, in the strict sense that it provides no > useful functionality or understanding of the language (ie the query > language) to describe its syntax in DAML+OIL as opposed to, say, BNF. > All that this enables a hypothetical DAML reasoner to do is to parse > the expressions of the query language. Using an ontology language for > parsing seems a very poor design decision; at the least, one that > should be discussed on its merits rather than simply assumed to be > somehow a Good Thing. I agree that there isn't any particular point to be made in using current DAML+OIL as opposed to BNF; but there is a point to be made by using *some* formal description of the syntax in addition to the examples and some prose. DAML is the formalization we're working on, and I appreciate the effort of trying to apply it to the task at hand. For example, I'm learning something from the points you raise below... We could go back and formally specify syntax and semantics for some BNF, with all the hairy internationalization and other interoperability issues, but that would seem to be quite a distraction. > (b) actively misleading, in the sense that it suggests that the > purpose of DAML+OIL is to be a syntax specification language, which > as far as I was aware wasn't ever even close to the intended goal of > the project; DAML is an effort to build an agent markup language; surely one of the things agents will need to talk to each other about is syntax. Perhaps applying the 2001-03 DAML+OIL language to the problem of syntax description is a stretch; but what better way to figure out what DAML needs next than to apply the current spec to the problems at hand and see what comes up? > (c) based on a basic misapprehension about the nature of descriptive > languages, in that part of the very idea of a *syntactic* > specification is that it describes domains of recursively defined > finite entities to which results such as the second recursion theorem > apply, whereas descriptive (assertional) languages like DAML+OIL (and > RDF and FOL) have an extensional semantics which is (because of > Goedel incompleteness) inherently unable to fully capture the notion > of finiteness or recursion. I'm afraid I'm guilty of this misapprehension. You have raised this point about the inability of FOPL to express finiteness/recursion a number of times now, and I have attempted to research it to the point where I understand, but I'm not there yet. If the 2001-03 DAML+OIL thingy can't express finiteness nor recursion, I'm interested in figuring out what we could layer on top to give DAML the ability to express it. > >We chuckled on the phone about what an obscure mechanism it is > >for communication in the group... > >but I hope each of us has at his/her disposal some tools > >that render DAML+OIL intelligible to us in some familiar > >notation/interface. > > I'm afraid I do not have access to any that I know how to use. I > wish there was one, indeed. Do you know of any? As I said in a subsequent message, I find rendering DAML as RDF/n3 helps me understand it; there's an online conversion service... http://swag.webns.net/n3tordf (it converts in both directions) I've implemented the basics of reading/writing RDF in KIF syntax in a way that could be integrated into this online service, if you're interested; (the source is also available, and I could perhaps help you install it; I think there are some issues with the python XML tools and the mac platform, though). As Danbri pointed out in his follow-up The FRODO RDFSViz Tool http://www.dfki.uni-kl.de/frodo/RDFSViz/ is available... but I'm not sure it pays attention to RDF vocabularies other than RDFS, so I'm not sure how applicable to DAML it is. I think protoge, oiled, etc. are also available, though I don't have first-hand experience with them. -- Dan Connolly, W3C http://www.w3.org/People/Connolly/
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