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Representing Disjunction and Quantifiers in RDF

Representing Disjunction and Quantifiers in RDF. on the paper by McDermott and Dou http://www.cs.yale.edu/~ddj/papers/ISWC02.pdf. Eyal Oren DERI 2004/04/23. Overview. RDF limitations Encoding predicate logic using reification Embedding PDDL in RDF. RDF. simple logical system

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Representing Disjunction and Quantifiers in RDF

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  1. Representing Disjunction and Quantifiers in RDF on the paper by McDermott and Douhttp://www.cs.yale.edu/~ddj/papers/ISWC02.pdf Eyal Oren DERI 2004/04/23

  2. Overview • RDF limitations • Encoding predicate logic using reification • Embedding PDDL in RDF

  3. RDF • simple logical system • assertions about things denoted with a URI • RDF: • <subject predicate object> • meaning of element depends on location in tag • no restrictions on value of properties (so arbitrary RDF node can be value of property) • easily merge different RDF sources

  4. Limitations of RDF • Limitations • no quantifiers, no negation, no disjunction • no arbitrary terms, only bags & sequences • Overcoming these: • extending RDF, user & developers opposition • embedding richer languagereification: using RDF to describe formulas in other language

  5. RDF triples corresponding RDF graph Example of reification Simple grammar Example sentence reification: the object of ‘second’is itself a triple

  6. encode terms, formulas, connectives (if, or) as RDF types: drs:If drs:antecedent drs:consequent drs:Atomic_formula drs:Term_seq drs:Functional_Term (P→Q) →R: Approach loves(Fred, Sally)<top rdf:type drs:Atomic_formula><top rdf:subject Fred><top rdf:pred loves><top rdf:obj Sally>

  7. Example functional terms child(C,M,F) child(Bates, mother(Bates), father(Bates))

  8. Quantifying Variables • introduce anonymous RDF variable • encode the properties of this variable (and the quantification) in the embedded language • forall X:Person → moralAgent(X) <var_1 rdf:Type Var><var_1 drs:name “x”><var_1 drs:type Person>

  9. Application to WebPDDL • extended PDDL (planning domain definition language) • “could be used to describe web services” • agent-centered • actions (an agent can take) • preconditions (for that actions) • effects (of that actions) • tractability not by limiting the syntax but: • every domain can set (computational) requirements, giving reasoners the opportunity to resign • WebPDDL ↔ RDF (DAML+OIL)

  10. Relevance to WSMO • about PDDL: interesting • about embedding logic in RDF • it is ‘just’ a syntactic embedding • looks awkward and very verbose • why use RDF in the first place • maybe I don’t understand the problem

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