1 W3C Rules Interchange Format Basic Logic Dialect Chris Welty IBM Research & RIF WG co-Chair.

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W3C Rules Interchange FormatBasic Logic Dialect

Chris Welty

IBM Research &

RIF WG co-Chair

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Rules, rules, rules…

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The Web Standards

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Semantic Web Layer Cake V1

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Semantic Web Layer Cake Vpast

IRI/Unicode

RDF

RDFS

OWL

Rules

Logic

Proof

Trust

Signature

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Semantic Web Layer Cake Vpresent

IRI/Unicode

RDF

RDFS

Rules

Logic Framework

Trust

Encryption

Proof

OWL

SP

AR

QL

Signature

Standards

RulesRDFS

Rules

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RIF Background

• Semantic web approach– interoperability requires a formal semantics

• The OWL WG approach– Start with something (DAML+OIL)

• Literally hundreds of rule system implementations– JSR-94, ISO-Prolog, CLIPS, OPS…– http://www.w3.org/2005/rules/wg/wiki/List_of_Rule_Systems– Already several “SW” rule languages

• SWRL, RuleML, WRL, SWSL, KAON2, TRIPLE, JenaRules…– Everyone wants “their” system/technique/theory to be the SW

rule standard• Workshop April ‘05

– http://www.w3.org/2004/12/rules-ws/– Outcome: Nash Equilibrium…

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Wherefore the RIFt(s)?• OWL DL < OWL < FOL

– Original idea to add full first-order at the logic level– Semantic web very “open world”

• Most back-end DBs support closed queries• Many rule systems have non-FO features

– CWA/NAF– Procedural Attachment– Rule ordering– Non-monotonicity… can’t be layered on OWL

• Not a strict SW layering already– OWL restricted dialects (DL) not layered on (all of) RDF/S

semantics– RDF & RDFS not layered at all

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Enter the Vendors

• “Rule systems Vendors”– $1B/year existing market– iLog, Fair Isaac, Haley, …

• Database vendors– Oracle, IBM

• OMG PRR effort– Simple production rules– Event-condition-action– Vendors understand the value of standardization– Interchange already a priority– …a common semantics?

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“One must understand, [rule systems] include a version of negation that is

operationally well-defined. The problem is to make semantic sense of it.”

Fitting, 1999

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Approach 1

• Define a super-language so expressive that any language can be translated to/from it– The CL and IKL approach

@deprecated: infeasible for this group, as major differences appeared irreconcilable (e.g. non-mon vs. mon)

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Approach 2

• Define a core language that accounts for the intersection of all rule language capabilities– E.g. Horn, datalog, …

@postponed: The production rule, logic programming, and FO core is not clear

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Approach 3

• Define a logic-based core and a separate production-rule core. If there is an intersection, define the common core (which may possibly be just a syntax)@version: 0.1 BLD

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Approach 3a

• Define a framework in the form of a menu of syntactic and semantic features that can be combined into dialects– @version 0.0.1 (FLD)

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Credits

• BLD Editors– Michael Kifer (U. Stonybrook), Harold Boley (NRCC)

• Active WG members– Adrian Paschke (REWERSE), Axel Polleres (DERI),

Dave Reynolds (HP), Gary Hallmark (ORACLE), Hassan Aït-Kaci (ILOG), Igor Mozetic (JFI), John Hall (OMG), Jos de Bruijn (FUB), Leora Morgenstern (IBM), Mike Dean (SRI), and Stella Mitchell (IBM)

• WG Team– Chris Welty (IBM), Christian de Sainte Marie (ILOG),

and Sandro Hawke (W3C/MIT)

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BLD Overview

• Definite Horn rules – Disjunction of atoms with exactly one positive literal

• Equality, functions, and a standard first-order semantics

• Syntactic features – objects and frames– internationalized resource identifiers (IRIs) as

identifiers– XML Schema data types and builtins

• XML (1.0) syntax with normative XMLS definition• Non-normative presentation syntax• Metadata and imports

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Symbols

• Used to identify constants, variables, functions, predicates

• "literal"^^<symspace-identifier>– Notable symbol spaces: xsd:string, rif:local,

rif:iri– “Chris”^^<xsd:string>– “

http://www.w3.org/1999/02/22-rdf-syntax-ns#type”^^<rif:iri>

– “Person1”^^rif:local

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Rules

• IF <condition> THEN <conclusion>– <condition> aka rule body, antecedant– <conclusion> aka rule head, consquent

• BLD rule:– (Forall var* <conclusion> :- <condition>)– Conclusions may contain conjunction– Conditions may contain conjunction, disjunction, and

existential

• Restrictions on conclusion– No existential, disjunction, external functions

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Horn Extensions

• Functions and external calls

• Equality (in conclusion and condition)

• Frames– Objects with slots and values– Special syntactic treatment of type and

subclass

• Named argument functions and predicates– However all arguments must be provided

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Structure

• Rules occur in GroupsGroup( (Forall ?x _Q(?x) :- _P(?x))

(Forall ?x _Q(?x) :- _R(?x)) )

• Groups occur in DocumentsDocument(

Group((Forall ?x _Q(?x) :- _P(?x))

(Forall ?x _Q(?x) :- _R(?x)))

Group((Forall ?y _R(?y) :- ex:op(?y))))

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Simple ExampleDatabase mapping

Document( Prefix(dbp http://dbpedia.org/property/)Prefix(my http://mydata.org/resource#)Prefix(rdfs http://www.w3.org/2000/01/rdf-schema#)Group ( Forall ?mname ?aname ?movie ?actor

my:actorIn(?aname ?mname) :- And( dbp:starring(?movie ?actor)

rdfs:label(?movie ?mname)rdfs:label(?actor ?aname))))

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my:actorIn(?aname ?mname) :- And(?movie[dbp:starring -> ?actor

rdfs:label -> ?mname] ?actor[rdfs:label ?aname])))

Simple Example w/ FramesDatabase mapping

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my:actorIn(actor->?aname movie->?mname) :- And(?movie[dbp:starring -> ?actor

rdfs:label -> ?mname] ?actor[rdfs:lasbel ?aname])))

Named Arguments

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And (Exists ?Buyer (cpt:purchase(?Buyer ?Seller cpt:book(?Author bks:LeRif) curr:USD(49))) ?Seller=?Author )

<And><formula><Exists><declare><Var>Buyer</Var></declare> <formula><Atom><op><Const type="&rif;iri">&cpt;purchase</Const></op> <args ordered="yes"><Var>Buyer</Var> <Var>Seller</Var> <Expr><op><Const type="&rif;iri">&cpt;book</Const></op> <args ordered="yes"> <Var>Author</Var> <Const

type="&rif;iri">&bks;LeRif</Const></args> </Expr> <Expr><op><Const type="&rif;iri">&curr;USD</Const></op> <args ordered="yes"> <Const type="&xsd;integer">49</Const></args> </Expr> </args> </Atom></formula> </Exists></formula> <formula><Equal> <side><Var>Seller</Var></side> <side><Var>Author</Var></side> </Equal></formula></And>

XML Syntax

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Metadata

• Can hang off any “class element”

<And><meta> <Frame> <object><Const type="rif:local">pd</Const></object> <slot ordered="yes"> <Const type="&rif;iri">&dc;publisher</Const> <Const type="&rif;iri">&w3;W3C</Const> </slot> </Frame> </meta>

<formula>...</formula></And>

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Metadata


<Group><meta> <Frame> <object><Const type="rif:local">pd</Const></object> <slot ordered="yes"> <Const type="&rif;iri">&dc;publisher</Const> <Const type="&rif;iri">&w3;W3C</Const> </slot> </Frame> </meta>

...</Group>

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Metadata


<Document><meta> <Frame> <object><Const type="rif:local">pd</Const></object> <slot ordered="yes"> <Const type="&rif;iri">&dc;publisher</Const> <Const type="&rif;iri">&w3;W3C</Const> </slot> </Frame> </meta>

...</Document>

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Status

• RIF BLD to Last Call June 23

• RIF RDF&OWL to Last Call June 23

• Last call indicates “final version for external review”

• w3.org/2005/rules

1 W3C Rules Interchange Format Basic Logic Dialect Chris Welty IBM Research & RIF WG co-Chair.

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