status: still drafty; meeting is adjourned, intend to fill in pointers to more of the presentations. $Date: 2000/08/13 16:13:34 $
Mike Dean, BBN; PI for DAML Integration
Tom Martin, Schafer Corp; support to Jim Hendler DAML, TASK, HORUS
Brian Kettler, ISX; PI for HORUS Initiative
Jeff Heflin, University of Maryland; SHOE
Deborah McGuinness, Stanford Knowledge Lab
Ora Lassila, Nokia Research Center; Agent Technologies
Dan Brickley, University of Bristol, W3C Visiting Fellow
Massimo Marchiori, University of Venice & W3C
Tim Berners-Lee, MIT/W3C
Stefan Decker, Stanford
Lynn Stein, MIT/LCS
Dan Connolly, MIT/W3C
Ralph Swick, MIT/W3C
w/Sergey Melnik
wants n-ary relations, ordering of relations
Lynn: why is order so important as to be part of the base, and not say synonomy, and transitivity?
Stefan: transitivity requires computation, which we wanted to avoid at the lowest level. Ordering is motivated in part by UML.
Tim: How much effort to produce an RDF syntax canonicalizer using XSLT? Dan: not much, ~40 hours.
Ora: can do this easily with a set of SAX event handlers that output canonicalized RDF. I have an RDF parser in Common Lisp which I intend to contribute to the DAML community.discussion of oil:subClassOf
DanC writes:
type(x,AandB)
[] -- rdf:type --> oil:AND
-- lhs --> A
-- rhs --> B
see Dan's notes Revision: 1.12 of Date: 2000/07/19 09:21:40 by Author: connolly (was then known as "hs78", but Dan expanded that into an explanation of his use of XSLT to extract RDF from XHTML pages.)
outline:
expect to release some tools to the DAML community:
TSE Ontology and risk path analyser
see GINF page
Knowledge Base
includes other Knowledge Bases
contain rule objects
rule objects have head & tail objects
head & tail have terms
terms have subject, predicate, and objects
DanC: this model relies on closed world to know that an object is not a variable.
Tim: note that in an RDF model, you can remove any triple and the remainder will remain true.
DanC: want the database to be "sound" under deletion of arcs.
Tim: note that RDF implicitly has the existential quantifier; The subject of an RDF statement is implicitly said to exist.
Mike: how do you account for temporal data?
DanC: hard problem.
Tim: can associate expiration dates via HTTP.
http://www-ksl-svc.stanford.edu:5915/ - main ontolingua server
http://www.ksl.stanford.edu/software/chimaera/ - chimaera - a merging and diagnostic ontology environment
DanC:
must model this such that deleting one of the premise arcs doesn't lead you to incorrect conclusions. You will know less about some of the objects, but you will know that there is something about which you don't know anything.
Stefan: It is not completely correct to view RDF as a conjunction when modelling rules.
DanC: quoting is the technique to express the two levels together.
Massimo: adding a Cardinality property to Stefan's representation will resolve the monotonicity.
Jeff: when negation is added, does this soundness still hold?
Dan: consider 'it is not raining today'
{subject, x, today}, {predicate, x, weatherOf}, {object, x, raining}, {implies, x, false}
If you delete the 'implies' arc, all you have left is "there is a sentence that says it is raining today".
Tim: note that you don't have to reify the {implies, x, false} statement.
Jeff expresses concern about the syntax for reification.
Tim: RDF is the form for exchanging on the Web, should we have a short-hand form for e-mail, irc, whiteboard?
DanC: there will be SVG tools that let us draw the same diagrams that we're drawing on the whiteboard. For exchange with colleagues, exploit one of the existing syntaxes; prolog, etc.; don't need more syntaxes.
Deborah: good to exploit existing KIF tools too.
Tim: need KIF with URIs. Consider adding namespaces to one of the existing KR languages?
DanC: Guha is doing a form of this with SQL.
inverse
maximum cardinality 1 (unique/equivalent)
Jeff: e.g. aboutEachPrefix
Proposition: DAML 0.x is RDF 1.0 + [parts of] RDF Schema + SHOE horn clauses w/o negation with just binary relations and without claim groups
layer 3: ?n-ary relations
layer 2: ?FOPC
layer 1: ?Horn clauses
layer 0: RDF 1.0 Model ?+Schema
DanC: don't want to require every application to have a first-order theorem prover.
Deborah: interoperability at the level of deductive closure; different logic systems will conclude the same things. Levels of compatibility: able to consume the facts without complaint, finding the explicit facts, making the same deductions.
Mike: anticipate adding digital signatures, temporal qualification, etc. later.
Deb: description logics discussion circa 1992 produced set of descriptive constructors; Knowledge Representation Specification System (KRSS) from Peter Patel-Schneider.
Deb: all new K-R papers must describe: syntax, denotational semantics, inference rules, computational complexity. Some things, like loom, are incomplete; there are true things they cannot infer.
Lynn: should not assume that the Description Logic community consensus represents a consensus of the full K-R community.
Deb: refer to description logics for a variety of notions of equality.
Tim: see also Identity in Web Design Issues.
ACTION: Dan write a rule meaning "equivalent for the purposes of xxx" [e.g. xxx == W3C Advisory Committee representative, a relation with cardinality 1.] (isomorphism)
Some chapter/section headings for an august paper:
semantics (stefan)
(authoring tools --Dan)
ACTION Mike: submit some uses cases
DanBri: [re: naming of relations] see Philippe Martin, "Propositions of Conventions and Ontologies for the Resource Description Framework".
** Ralph: propose a different term than namespace or schema for.
**DanBri: Take to system team "please separate (in the master list) obsolete mailing lists from real ones and make semantic-web@ obsolete"
"preceded by itself within quotes is obsolete" preceded by itself within quotes is obsolete.
<RalphS> use www-rdf-logic@w3.org for open
discussion; archived
<RalphS> Note irc.w3.org:6665 channel #sw is also
open
Dan: please agree to publish Web addresses for all your facts furthermore, please agree to only make monotonic changes to the content at those Web addresses.
RESOLVED: obsoletes(x, y) = y makes x obsolete http://www.w3.org/2000/07/document-maintenance/#obsoletes
RESOLVED: sublanguage(x, y) = x is a sublanguage of y http://www.w3.org/2000/07/document-maintenance/#sublanguage (see timbl for examples/semantics)
PROPOSED: rdfExtractor(x, y) = y will extract RDF from x http://www.w3.org/2000/07/document-maintenance/#rdfExtractor
note well:
for inverseof, see oil:inverseRelationOf