Rule-based reasoning in the Semantic Web

Rule-based reasoning in the Semantic WebFulvio Corno, Laura FarinettiPolitecnico di TorinoDipartimento di Automatica e Informaticae-Lite Research Group – http://elite.polito.itOutline Motivation SWRL RIFF. Corno, L. Farinetti - Politecnico di Torino2Motivation Classical reasoning operations in OWL only allow very limited use cases Consistency Class properties and relationships Instance classification How to to more complex reasoning tasks? E.g., inferring properties of instances depending on other instance properties?F. Corno, L. Farinetti - Politecnico di Torino3Types of rules Production Rules (or Inference Rules) IF condition THEN action Logical predicates Executed upon explicit request, starting from a stateless initial condition Event-Condition-Action rules “Reactive” execution to detect and react to incoming events and process event patterns Usually running in parallel to the application, reacting when events occur, usually in a stateful mannerF. Corno, L. Farinetti - Politecnico di Torino4Rule-based reasoning Forward chaining Backward chaining RETE Algorithm Goal-directed reasoningF. Corno, L. Farinetti - Politecnico di Torino5Forward chaining Forward chaining starts with the available data and uses inference rules to extract more data until a goal is reached.  An inference engine using forward chaining searches the inference rules until it finds one where the antecedent (If clause) is known to be true. When found it can conclude, or infer, the consequent (Then clause), resulting in the addition of new information to its dataF. Corno, L. Farinetti - Politecnico di Torino6Backward chaining Backward chaining starts with a list of goals (or a hypothesis) and works backwards from the consequent to the antecedent to see if there is data available that will support any of these consequents. An inference engine using backward chaining would search the inference rules until it finds one which has a consequent (Then clause) that matches a desired goal. If the antecedent (If clause) of that rule is not known to be true, then it is added to the list of goals (in order for one's goal to be confirmed one must also provide data that confirms this new rule).F. Corno, L. Farinetti - Politecnico di Torino7Rule engines Drools (now Jboss Rules, own rule format) http://www.jboss.org/drools SweetRules (RuleML, SWRL, others) http://sweetrules.semwebcentral.org/ Jena 2 (own rule format) http://jena.sourceforge.net/inference/ Jess (own rule format) http://www.jessrules.com/ Pellet Bossam …F. Corno, L. Farinetti - Politecnico di Torino8Outline Motivation SWRL RIFF. Corno, L. Farinetti - Politecnico di Torino9Semantic Web Rule Language (SWRL) Not an official W3C Recommedation Application to OWL of the RuleML (http://ruleml.org/) languages Extends OWL language by providing Horn clauses Defines an extension of the OWL model-theoreticsemanticsF. Corno, L. Farinetti - Politecnico di Torino10