|2007-11-09 -||Version 0.9|
|2008-08-24 -||Version 0.91|
This is the specification of Defeasible RuleML 1.0.
Based on previous work including Courteous Logic Programs, Defeasible RuleML was first exemplified in the 'Rationale' RuleML paper and later revised for RuleML 0.87, 0.9, 0.91, and 1.0.
Defeasible RuleML 1.0 uses (control-)relationship Atoms applying a binary control relation
<Rel iri="http://ruleml.org/1.0/vocab/control#Overrides"/>to rule labels, where http://ruleml.org/1.0/vocab/control#Overrides is a reserved IRI representing overriding between the labeled rules. Such overriding superiority is 'hard' in the sense of, e.g., committed choice languages, where failure of subsequent computation will not lead to a revision of a choice between rules (e.g., there will be no backtracking to an earlier Overrides choice). In an extension of Defeasible RuleML 1.0, a 'soft' variant of superiority allowing such revision could be introduced by replacing the IRI http://ruleml.org/1.0/vocab/control#Overrides, for (irreversibly) overriding superiority, with http://ruleml.org/1.0/vocab/control#Dominates, for (reversibly) dominating superiority. Similarly, other extensions can introduce (RuleML-internal or -external) reserved IRIs for expressing further superiority-variant semantics such as time- and/or location-sensitive overriding. The superiority relationships can be defined both by facts and rules, the latter permitting conditional superiority. In Defeasible RuleML documents in which only unconditional overriding is needed, an Overrides element
<Overrides> ... ... </Overrides>can be used as a special atom that shortcuts the regular Atom element
<Atom><Rel iri="http://ruleml.org/1.0/vocab/control#Overrides"/> ... ... </Atom>applying http://ruleml.org/1.0/vocab/control#Overrides as its relation.
Introductions to (earlier versions of) Defeasible RuleML were given, e.g., in the context of business contracts and DR-DEVICE.
Various sample Defeasible RuleML documents have been prepared and maintained; some exemplify features of Defeasible RuleML and are useful didactically while others are mostly for testing puposes.
A use case of Defeasible RuleML has been developed at Carlo-rbase-1.0.ruleml (cf. wiki history). The 'Carlo use case' version accessible to validators is being kept at carlo-rbase.ruleml.
The schema specification of Version 1.0 has been created at defeasible.xsd and dr-device.xsd.
This specification is being developed in collaboration with OASIS, in particular the LegalRuleML TC.
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