Semantic Web Rule Language

For the proposed railway in Sydney, Australia, see South West railway line, Sydney.

SWRL (Semantic Web Rule Language) is a proposal for a Semantic Web rules-language, combining sublanguages of the OWL Web Ontology Language (OWL DL and Lite) with those of the Rule Markup Language (Unary/Binary Datalog).

The specification was submitted in May 2004 to the W3C by the National Research Council of Canada, Network Inference (since acquired by webMethods), and Stanford University in association with the Joint US/EU ad hoc Agent Markup Language Committee.

SWRL has the full power of OWL DL, but at the price of decidability and practical implementations.[1]

Rules are of the form of an implication between an antecedent (body) and consequent (head). The intended meaning can be read as: whenever the conditions specified in the antecedent hold, then the conditions specified in the consequent must also hold.

Contents

Example

Human Readable Syntax

hasParent(?x1,?x2) ∧ hasBrother(?x2,?x3) ⇒ hasUncle(?x1,?x3)

XML Concrete Syntax

The XML Concrete Syntax is a combination of the OWL Web Ontology Language XML Presentation Syntax with the RuleML XML syntax.

 <ruleml:imp> 
  <ruleml:_rlab ruleml:href="#example1"/>
  <ruleml:_body> 
    <swrlx:individualPropertyAtom  swrlx:property="hasParent"> 
      <ruleml:var>x1</ruleml:var>
      <ruleml:var>x2</ruleml:var>
    </swrlx:individualPropertyAtom> 
    <swrlx:individualPropertyAtom  swrlx:property="hasBrother"> 
      <ruleml:var>x2</ruleml:var>
      <ruleml:var>x3</ruleml:var>
    </swrlx:individualPropertyAtom> 
  </ruleml:_body> 
  <ruleml:_head> 
    <swrlx:individualPropertyAtom  swrlx:property="hasUncle"> 
      <ruleml:var>x1</ruleml:var>
      <ruleml:var>x3</ruleml:var>
    </swrlx:individualPropertyAtom> 
  </ruleml:_head> 
 </ruleml:imp>

RDF Concrete Syntax

It is straightforward to provide such an RDF concrete syntax for rules, but the presence of variables in rules goes beyond the RDF Semantics.[2] Translation from the XML Concrete Syntax to RDF/XML could be easily accomplished by extending the XSLT transformation for the OWL XML Presentation syntax.

Implementations

Caveat: Reasoners do not support the full specification because the reasoning becomes undecidable. There can be three types of approach: translate SWRL into First Order Logic (Hoolet) and demonstrate reasoning tasks with a theorem prover; translate OWL-DL into rules and give the rules to a forward chaining engine (Bossam) (this approach cannot cover the full expressivity of OWL-DL due to many incompatibilities between Description Logic and Horn Rule formalisms); expand an existing OWL-DL reasoner based on the tableaux algorithm (Pellet).

Bossam Hoolet Pellet
SWRL/OWLX Parser Yes  ?  ?
SWRL/RDF Parser Yes  ? Yes
Math Built-Ins Partial  ? Yes
String Built-Ins Partial  ? Yes
Comparison Built-Ins  ?  ? Yes
Boolean Built-Ins  ?  ? Yes
Date, Time and Duration Built-Ins  ?  ?  ?
URI Built-Ins  ?  ? Yes
Lists Built-Ins  ?  ? No
Licencing Free/closed-source Free/open-source Free/open-source

Comparison with Description Logic Programs

Description Logic Programs (DLPs) are another proposal for integrating rules and OWL.[3] Compared with Description Logic Programs, SWRL takes a diametrically opposed integration approach. DLP is the intersection of Horn logic and OWL, whereas SWRL is (roughly) the union of them. In DLP, the resultant language is a very peculiar looking description logic and rather inexpressive language overall.

See also

References

  1. ^ Bijan Parsia; et al. (2005) (PDF). Cautiously Approaching SWRL. http://www.mindswap.org/papers/CautiousSWRL.pdf. Retrieved 2006-07-29. 
  2. ^ Mei, Jing; Harold Boley (2006). "Interpreting SWRL Rules in RDF Graphs". Electronic Notes in Theoretical Computer Science (Elsevier) (151): 53–69. http://www.is.pku.edu.cn/~mayyam/papers/Interpreting%20SWRL%20Rules%20in%20RDF%20Graphs.pdf. Retrieved 2006-07-29. 
  3. ^ Description Logic Programs: Combining Logic Programs with Description Logic, WWW 2003.

External links