a web rules wg charter focus strawman proposal version 1.1, april 30, 2005 this version prepared by:...
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A Web Rules WG Charter Focus
Strawman ProposalVersion 1.1, April 30, 2005
This Version Prepared by:Benjamin Grosof, Harold Boley, Michael Kifer, and Said Tabet
of The RuleML Initiative (http://www.ruleml.org).Incorporating Comments by Ed Barkmeyer.
***Further revisions to be incorporated from community discussion.***
Modified from earlier version in RuleML Position Paper [96] of the W3C Workshop on Rule Languages for Interoperability, 27-28 April 2005.
Responsive to the discussion from that Workshop, and from the WSMO-RuleML-SWSI Face-to-Face Meeting of 26 April 2005.
“WG” above = W3C Working Group
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The Web Rule Language in its Context
XML
URIUnicode
RDF(S)
OWLRules
FOL++
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Semantic Interoperability Principles - high level
• Conclusions sanctioned do not depend on how executed, e.g., forward chaining has same semantics as backward chaining
• “Reaction” rules, that perform side-effectful actions, have a semantics which cleanly extends the basic case of rules that do not.
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Focus Overall of WG• Kernel based on logical KR
– Semantics, syntax, layering: for that kernel– Rudimentary rule management: e.g., queries, answers, premises, conclusions, updates to
premises, ruleset definition, importation of rules, simple versioning, simple provenance
•Use Cases from Business Processes, Services– Policies, in particular– Support Semantic Web Services requirements, in particular
• Integrate Rules and Ontologies– Interoperate with OWL, in particular– Represent Ontologies as Rules, in particular
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Rule Communities Served
• Semantic Web – general, using XML and/or RDF encoding
– RDF- and OWL-centric, in particular– Logic Program based, in particular
• Business Rules– general, based on existing rule-based– Production Rules, in particular
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Kernel KR FocusDeclarative Logic Programs expressiveness including 1. Datalog Horn LP (N-ary predicates supported)
2. + scoped default negation applied to atoms a. simple extensional
b. more general (allowing inferential chaining to establish the atom in question -- subset of, or full, Well Founded semantics)
3. + procedural attachments (external calls) a. actions (side-effectful – external) b. tests (side-effect-free queries) 4. + logical functions, incl. for object creation, skolemization
a. limited initially (to ensure finite/tractable forward inferencing)
b. more general (e.g., for backward chaining, “sugar” features)
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Kinds of Rules & Rule Systems Translatable/Reducible to Kernel
Most other wish-list features can be expressively reduced to this core KR abstraction, for which
Situated Ordinary Logic Programs can provide the semantics theory
• OWL: large subset, • OWL ontology integration via overlap of LP with Description Logic (e.g., use Description Logic Programs V2, with integrity constraints, skolemization, equality, passing of derived facts)• SWRL: large subset • Production Rules cf. PRRuleML: large subset (Production Logic Programs)• Decision trees• Decision tables• “Sequential” rules cf. PRR: [**probable, need to understand
better]• Prolog: the pure subset (which is large)• SQL relational databases: large subset (incl. all core)• Event-Condition-Action rules: large subset
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Those are translatable/reducible because the following are …
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Additional “Sugar” Features that are
Translatable/Reducible to KernelMost other wish-list features can be expressively reduced* to this core KR abstraction, for
which Situated Ordinary Logic Programs can provide the semantics theory (* with tractability, known techniques).
E.g., much or all of the expressiveness in the following.
•RDF facts •Frame syntax•Slotted syntax•Lists•(N-ary predicates if restrict core to 2-ary)•RDFS-DL simple ontologies•Datatyping: basic
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Sugar Features II•“Else” part of if-then-else•Courteous prioritized defaults, incl. declarative priorities, limited strong/classical
negation, prioritized conflict handling, paraconsistency
robustness
•Default inheritance cf. Object Oriented programming, “frame” languages
•“Hilog” – quasi higher order syntactic sugar•Lloyd-Topor•Integrity constraints that report violations•Anonymous existentials, blank-nodes, limited
skolemization•“Crud” – create update delete, cf. Production Rules (restricted)
•“Assert”, and basic “retract”, cf. Production Rules (restricted)
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Sugar Features III
•Reification, basic•User equality, basic aspects •Equations, basic•Built-ins (side-effect-free functions/operators, read/write)
•Access to surrounding object-oriented data environment, cf. OO Production Rules
•Ontological context translation & mediation•Contextual selection conditions for whole rulesets•“Rules flow”: some (e.g., sequencing of rule groups)
•… probably some more things we forgot to list here …
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The Web Rule Language in its Context
XML
URIUnicode
RDF(S)
OWLRules
FOL++
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Layering Relationships wrt existing Semantic Web Standards
subsumes (expressively) layers-on (makes use of) overlaps-with (expressively)
RDFS-DL
XML
OWL-DLDLP
Rules KernelSWRL
overlaps
RDF
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Sugar Features vs. Kernel
•“Sugar-enhanced” Languages can be translated into the kernel.– I.e., Sugar Features can be implemented/supported
via translators– Including as “best practice”, etc.
•Could consider doing some of them as part of WG proper– E.g., basic set of datatypes
•… But it’s not as crucial
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Deliverables Desired
•Abstract syntax•Semantics•Layering definitions: e.g., Datalog Horn layer
•Concrete syntax: – Markup syntax in XML– RDF (e.g., RDF/XML) – Human-readable presentation (non-XML) syntax
•UML/MOF metamodel•Some light ontology about rudimentary rule
management, incorporated into the above– E.g., to enable representing provenance, or expressive
restrictions met, about a particular rulebase
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Supported Tasks & Kinds of Knowledge
•Policies: authorization, contracting, security, privacy, monitoring, advertising, regulations, governance, …
•Validation: integrity, notification, …•Business Processes, Workflows, Protocols, …
– Process modeling: Abstract State Machines, Pi-Calculus, …
•Semantic Web Services•Ontologies•Mediation: map between ontologies/contexts •…
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