Candidate Tech: SWRL W3C Workshop on Rules April, 2005 Bijan - - PowerPoint PPT Presentation

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Candidate Tech: SWRL W3C Workshop on Rules April, 2005 Bijan - - PowerPoint PPT Presentation

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mindswap maryland information and network dynamics lab semantic web agents project Candidate Tech: SWRL W3C Workshop on Rules April, 2005 Bijan Parsia mindswap maryland information and network dynamics lab semantic web agents project

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mindswap

maryland information and network dynamics lab semantic web agents project

Candidate Tech: SWRL

W3C Workshop on Rules April, 2005 Bijan Parsia

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Interoperate with what?

  • “Legacy” rules systems

– Within rule “families”

  • E.g., ISO Prolog

– Between rule “families”

  • E.g., RuleML
  • The Non-Semantic Web

– Standardize what?

  • HTTP/HTML/XML support?
  • XQuery as Functional/Logic Programming language?
  • Process languages? Web Services?
  • The Semantic Web
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The Semantic Web Requirement

  • Rules for the Semantic Web

– Conform to abstract principles

  • URI use, (perhaps) open world, XML syntax, distributability,

layering/semantic compatibility

– Conform to existing standards

  • RDF and OWL
  • SPARQL (not quite existing)

– Various sorts of non-conformance

  • To a (small) subset of OWL (e.g., RDF, RDFS, DLP)
  • Different semantics (not just extensions)
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OWL Compatibility

  • Reuse existing ontologies

– With their full expressivity

  • No shadow ontologies or radically incompatible extensions
  • OWL has (limited) rules!
  • Augment existing ontologies

– Extend OWL expressivity

  • Four possibilities

– Subset (DLP, Horn-SHIQ) – Hybrid (AL-Log, Carin, DL-Safe rules) – Superset (SWRL) – Alter (Classic style rules, other non-mon extensions)

  • The first three are subsumed by SWRL*
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SWRL

  • Basic idea:

– Horn rules where… – predicate functors are OWL-DL class, datatype, or property names

  • (class expressions can be used, in principle)

– with first order semantics

  • (i.e., SWRL is a fragment of FOL)

– XQuery inspired built-ins

  • A hint:

– rdfs:subClassOf and rdfs:subPropertyOf are syntactically restricted (material) implication – ruleml:imp generalizes these

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Example DL KB

Computer ⊆ Product Monitor ⊆ Product Computer ⊆ ∃hasCPU.CPU CPU ⊆ ∃hasSpeed.CPUSpeed Customer ⊆ Person SalesService = Service & ∃sells.Product ExpensiveComputer = Compter & ∃hasPrice.HighPrice

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AL-Log style

convenient(?cust, ?serv) :-

livesIn(?cust, ?loc), fastDelivery(?serv, ?loc), Customer(?cust), SalesService(?serv). (where no binary term appears in the OWL

  • ntology, though they may be characterized

by other AL-Log rules)

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Carin style

discountAvailable(?cust, ?printer) :-

previouslyBought(?cust, ?comp), sameBrand(?comp, ?printer), hasPrice(?comp, ?price), Customer(?cust), Printer(?printer), Computer(?computer), HighPrice(?price)

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DL-Safety

  • Given an OWL-DL ontology O and a

Datalog program P:

– A rule r is strongly DL-safe if each variable in r

  • ccurs in a non-DL atom in the rule body.

– P is strongly DL-safe if all its rules are

  • http://www.fzi.de/KCMS/kcms_file.php?act

ion=link&id=484

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SWRL in toto

  • Only safety condition is standard Datalog safety

– I.e.,variables in the head must appear in the body – Merely syntactic; no expressive consequence

  • No decision procedure
  • No native reasoners (yet)

– Translate-to-FOL & use full FOL reasoner (see Ian) – DL Safe rules covers a large (decidable) subset in a resolution framework – Convergence?

  • Inferable rules (rule redundacy, specificity; query

containment)

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Some SWRLing Issues

  • Syntax

– The Semantic desperately needs a sane and extensible syntactic framework – Same-syntax semantic extensions won’t cut it

  • OWL Full

– Some parts easy, some parts hard

  • (Some parts undesirable!)
  • N-ary predicates
  • Non-mon features
  • Modularity
  • SWRL vs. SWRL FOL
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  • http://www.w3.org/Submission/2004/SUBM-

SWRL-20040521/

  • http://kaon2.semanticweb.org/

– Reduces The SHIQ description logic to disjunctive datalog; defines a horn fragment of SHIQ; defines DL Safety; has decidable metamodeling; good stuff!

  • http://www.kr.tuwien.ac.at/staff/roman/asp_sw/

– Different approach to combining DL with Datalog which admits negation-as-failure for the rules

  • http://www.w3.org/2004/12/rules-ws/paper/71

– Framework subsuming SWRL, plus pointers to more decidable subsets.

  • Thanks: Evren Sirin, Bernardo Grau, Edna Ruckhaus,

Daniel Hewlett, Jordan Katz, Kendall Clark