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

2. Rules, rules, rules…

3. The Web Standards

4. Semantic Web Layer Cake V1

5. Semantic Web Layer Cake Vpast
Trust
Proof
Signature
Logic
Rules
OWL
RDFS
RDF
IRI/Unicode

6. Semantic Web Layer Cake Vpresent
Rules
Trust
Standards
Proof
Signature
Encryption
Logic Framework
SPARQL
OWL
Rules
Rules
RDFS
RDFS
RDF
IRI/Unicode

7. RIF Background Semantic web approach The OWL WG 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…
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
Outcome: Nash Equilibrium…

8. 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

9. Enter the Vendors “Rule systems Vendors” Database 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?

10. “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

11. 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)

12. 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

13. 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

14. Approach 3a
Define a framework in the form of a menu of syntactic and semantic features that can be combined into dialects
@version (FLD)

15. Credits BLD Editors Active WG members WG Team
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)

16. 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

17. Symbols Used to identify constants, variables, functions, predicates
"literal"^^<symspace-identifier>
Notable symbol spaces: xsd:string, rif:local, rif:iri
“Chris”^^<xsd:string> “
“Person1”^^rif:local

18. Rules IF <condition> THEN <conclusion> BLD rule:
<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

19. 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

20. Structure Rules occur in Groups Groups occur in Documents
Group( (Forall ?x _Q(?x) :- _P(?x))
(Forall ?x _Q(?x) :- _R(?x)) )
Groups occur in Documents
Document(
Group((Forall ?x _Q(?x) :- _P(?x))
(Forall ?x _Q(?x) :- _R(?x)))
Group((Forall ?y _R(?y) :- ex:op(?y))))

21. Simple Example Database mapping
Document( Prefix(dbp
Prefix(my
Prefix(rdfs
Group ( Forall ?mname ?aname ?movie ?actor 
my:actorIn(?aname ?mname) :-
And( dbp:starring(?movie ?actor)
rdfs:label(?movie ?mname)
rdfs:label(?actor ?aname))))

22. Simple Example w/ Frames Database mapping
Document( Prefix(dbp
Prefix(my
Prefix(rdfs
Group ( Forall ?mname ?aname ?movie ?actor 
my:actorIn(?aname ?mname) :-
And(?movie[dbp:starring -> ?actor
rdfs:label -> ?mname]
?actor[rdfs:label ?aname])))

23. Named Arguments Document( Prefix(dbp http://dbpedia.org/property/)
Prefix(my
Prefix(rdfs
Group ( Forall ?mname ?aname ?movie ?actor 
my:actorIn(actor->?aname movie->?mname) :-
And(?movie[dbp:starring -> ?actor
rdfs:label -> ?mname]
?actor[rdfs:lasbel ?aname])))

24. XML Syntax 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>
<Const type="&xsd;integer">49</Const></args>
</args>
</Atom></formula>
</Exists></formula>
<formula><Equal>
<side><Var>Seller</Var></side>
<side><Var>Author</Var></side>
</Equal></formula>
</And>

25. Metadata <And> <formula>...</formula> </And>
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>

26. Metadata <Group> ... </Group>
Can hang off any “class element”
<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>

27. Metadata <Document> ... </Document>
Can hang off any “class element”
<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>

28. 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