1. RuleML for the Semantic Web Harold Boley OntoWeb Kick-off WorkshopOntoWeb Kick-off Workshop, Heraklion, Greece, 13-15 June 2001 Revised: 17 July 2001 (joint work with Benjamin Grosof, Said TabetSaid Tabet, and Gerd WagnerGerd Wagner)

2. RuleML 1 Motivation (I) Rules in (and for) the Web have become a mainstream topic since – inference rules were marked up for E-Commerce identified as a Design Issue of the Semantic Web – transformation rules were used for document generation from central XML repository Rule interchange is becoming more important in Knowledge Representation (KR), especially in –Intelligent Agents –AI shells for knowledge-based systems

3. RuleML 2 Motivation (II) The Rule Markup Initiative has taken initial steps towards defining a shared Rule Markup Language (RuleML) for interoperation between ParticipantsRule Markup Initiative Participants RuleML permits forward (bottom-up) and backward (top-down) rules in XML for – deduction – rewriting – further inferential-transformational tasks

4. RuleML 3 Structure of the RuleML DTD Hierarchy Our system of DTDs (current version: 0.8) uses a modularization approach similar to XHTML in order to accomodate the various rule subcommunities The evolving hierarchy of RuleML DTDs forms a partial order with ruleml as the greatest element (a ruleml-rooted DAG) -- many ‘smallest’ elements Each DTD node in the hierarchy (conformance “lattice”) corresponds to a specific RuleML sublanguage: – ‘Union’ (join) of sublanguages reached via outgoing links: to smaller or equal nodes below – ‘Intersection’ (meet) of sublanguages via incoming links: from greater or equal nodes above

5. RuleML 4 The Module Hierarchy of RuleML DTDs urc-bin-data-ground-fact urc-bin-data-ground-log urc-bin-datalog bin-datalogurc-datalog ur-datalog ur-hornlog ur-equalog hornlog equalog datalog ur Rooted DAG will be extended with branches for further sublanguages URL/URI-like ‘ur’-objects ruleml RDF-like triples ur-datalog = join(ur,datalog)

6. RuleML 5 From traditional XML Representation to RDF-like Representation of RuleML Rules XML: N-ary, positional representation of rules; overspecification for non-sequential parts RDF: Binary, labeled representation of rules with nodes for resources and labels as explicit role names; Seq container needed for sequential parts RuleML: – Sequential parts from XML – Labeled parts from RDF

7. RuleML 6 You want to review rule principles You may look at Rule Based Systems Recommender Rule: Forward Markups Original RuleML markup with XHTML in body/head (English premise and semiformal conclusion): Challenge hypertext as one XHTML paragraph: If you want to review rule principles, you may look at Rule Based Systems premise conclusion

8. RuleML 7 Recommender Rule: Backward Markup may look at you Rule Based Systems want to review you rule principles Further formalized RuleML markup (still unanalyzed English relation and individual-constant names): conclusion premise

9. RuleML 8 Two-Way Relationship Between RuleML and RDF RDF in RuleML: – RDF triples as facts described by a DTD in the RuleML family – Example: Next slide RuleML in RDF: – RDF graphs and serializations for RuleML rules – Exemplified in previous slides

10. RuleML 9 RuleML Element of URC-Bin-Data-Ground-Fact DTD: RDF Triple as Very Special Rule Creator Ora Lassila RDF triple(predicate, subject, object) as atom predicate(subject, object) or rel(ur, ur|ind) "http://www.w3.org/Home/Lassila has creator Ora Lassila." (Creator, http://www.w3.org/Home/Lassila, Ora Lassila)

11. RuleML 10 Conclusions RuleML DTD 0.8, a system of DTDs, is available at http://www.dfki.de/ruleml/ indtd0.8.html ; sample files at http://www.dfki.de/ruleml/0.8/exahttp://www.dfki.de/ruleml/ indtd0.8.htmlhttp://www.dfki.de/ruleml/0.8/exa Further rule categories (e.g. integrity constraints and reaction rules) will be available via main RuleML page at http://www.dfki.de/ruleml http://www.dfki.de/ruleml Distributed KR can already be based on current DTDs -- using (XSLT) transformations to reach follow-up and Participants’ DTDsParticipants’