Outline

• Where RIF Came From
• What RIF Is (Rule Interchange Format)
• Extending RIF
• Why the Semantic Web Needs RIF

What is a Rule?

• Logic programming (LP), from Prolog (early 70s)
• Production Rules (PR), OPS5/Rete (late 70s)
• Automated Theorem Proving (ATP), (resolution, 1965)
• app-specific rule systems (eg mail handling, access control)
• Business Rules
• not natural language rules

A way of programming, and a way of not programming

Semantic Web Perspective

What does RIF do for the Semantic Web?

• A companion to RDFS and OWL -- another logic
• Can express different kinds of things
• A different way of thinking -- which many people want
• Data integration, ontology mapping, ad hoc reasoning
• ... even data processing (N3)

Business Rules Perspective

Thinking in terms of the business

• reduce vendor lock-in (portability)
• coordinating businesses, eg in a supply chain
• integrated decision support, eg in medical decisions

Diversity

Simplicity vs Research

• Different traditions
• Different technologies
• Different kinds of problems
• Different people

Dream vs Reality

The Plan

Start with a common core

1. Find out what rule systems have in common (60%)
2. Standardize that ("RIF Core")
3. Then work on extensions

Core must be truly extensible

More Details

Focus on translating to/from RIF

• So it's fine to be verbose XML
  • Nothing very pretty, for humans
• Implementation burden is on translators
  • Not necessary rule engine maintainers

Extensions may be incompatible

• Dialect == group of extensions that work well together
• Some standard, some non-standard

"Rule Interchange Format", not "Semantic Web Rule Language"

Timeline

• RuleML initiative, TimBL's cwm/n3 (Fall 2000)
• W3C Submissions (2004-2005): SWRL, SWRL-FOL, SWSL, WRL
• Workshop (April 2005), ~80 people
• F2F1 (December 2005) ~50 people
• Use Cases and Requirements (2006)
• F2F5, RIF Core WD1 (2007 Q1) ~ 20 people
• Production Rules, Builtins, etc (2008)
• F2F13, RIF Last Call (July 2009) ~ 15 people
• Candidate Recommendation (October 2009)
• W3C Recommendation (June 2010)

Community

• Business rules vendors
  • ILOG [now IBM] (chair), Fair Isaac, Oracle, TIBCO, JBoss...
• Commercial Research
  • IBM (chair), HP, ...
• Non-Commercial Research
  • NRC, Bolzano, DERI, MITRE, REWERSE, ...
• ... others
  • Betfair, OMG

RIF: XML Syntax for Rules

<!DOCTYPE Document [
  <!ENTITY ppl  "http://example.com/people#">
  <!ENTITY cpt  "http://example.com/concepts#">
  <!ENTITY dc   "http://purl.org/dc/terms/">
  <!ENTITY rif  "http://www.w3.org/2007/rif#">
  <!ENTITY func "http://www.w3.org/2007/rif-builtin-function#">
  <!ENTITY pred "http://www.w3.org/2007/rif-builtin-predicate#">
  <!ENTITY xs   "http://www.w3.org/2001/XMLSchema#">
]>

<Document 
    xmlns="http://www.w3.org/2007/rif#"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:xs="http://www.w3.org/2001/XMLSchema#">
  <payload>
   <Group>
    <id>
      <Const type="&rif;iri">http://sample.org</Const>
    </id>
    <meta>
      <Frame>
        <object>
          <Const type="&rif;local">pd</Const>
        </object>
        <slot ordered="yes">
          <Const type="&rif;iri">&dc;publisher</Const>
          <Const type="&rif;iri">http://www.w3.org/</Const>
        </slot>
        <slot ordered="yes">
          <Const type="&rif;iri">&dc;date</Const>
          <Const type="&xs;date">2008-04-04</Const>
        </slot>
      </Frame>
    </meta>
    <sentence>
     <Forall>
       <declare><Var>item</Var></declare>
       <declare><Var>deliverydate</Var></declare>
       <declare><Var>scheduledate</Var></declare>
       <declare><Var>diffduration</Var></declare>
       <declare><Var>diffdays</Var></declare>
       <formula>
         <Implies>
           <if>
             <And>
               <formula>
                 <Atom>
                   <op><Const type="&rif;iri">&cpt;perishable</Const></op>
                   <args ordered="yes"><Var>item</Var></args>
                 </Atom>
               </formula>
               <formula>
                 <Atom>
                   <op><Const type="&rif;iri">&cpt;delivered</Const></op>
                   <args ordered="yes">
                     <Var>item</Var>
                     <Var>deliverydate</Var>
                     <Const type="&rif;iri">&ppl;John</Const>
                   </args>
                 </Atom>
               </formula>
               <formula>
                 <Atom>
                   <op><Const type="&rif;iri">&cpt;scheduled</Const></op>
                   <args ordered="yes">
                     <Var>item</Var>
                     <Var>scheduledate</Var>
                   </args>
                 </Atom>
               </formula>
               <formula>
                 <Equal>
                   <left><Var>diffduration</Var></left>
                   <right>
                     <External>
                       <content>
                         <Expr>
                           <op><Const type="&rif;iri">&func;subtract-dateTimes</Const></op>
                           <args ordered="yes">
                             <Var>deliverydate</Var>
                             <Var>scheduledate</Var>
                           </args>
                         </Expr>
                       </content>
                     </External>
                   </right>
                 </Equal>
               </formula>
               <formula>
                 <Equal>
                   <left><Var>diffdays</Var></left>
                   <right>
                     <External>
                       <content>
                         <Expr>
                           <op><Const type="&rif;iri">&func;days-from-duration</Const></op>
                           <args ordered="yes">
                             <Var>diffduration</Var>
                           </args>
                         </Expr>
                       </content>
                     </External>
                   </right>
                 </Equal>
               </formula>
               <formula>
                 <External>
                   <content>
                     <Atom>
                       <op><Const type="&rif;iri">&pred;numeric-greater-than</Const></op>
                       <args ordered="yes">
                         <Var>diffdays</Var>
                         <Const type="&xs;integer">10</Const>
                       </args>
                     </Atom>
                   </content>
                 </External>
               </formula>
             </And>
           </if>
           <then>
             <Atom>
               <op><Const type="&rif;iri">&cpt;reject</Const></op>
               <args ordered="yes">
                 <Const type="&rif;iri">&ppl;John</Const>
                 <Var>item</Var>
               </args>
             </Atom>
           </then>
         </Implies>
       </formula>
     </Forall>
    </sentence>
    <sentence>
     <Forall>
       <declare><Var>item</Var></declare>
       <formula>
         <Implies>
           <if>
             <Atom>
               <op><Const type="&rif;iri">&cpt;unsolicited</Const></op>
               <args ordered="yes"><Var>item</Var></args>
             </Atom>
           </if>
           <then>
             <Atom>
               <op><Const type="&rif;iri">&cpt;reject</Const></op>
               <args ordered="yes">
                 <Const type="&rif;iri">&ppl;Fred</Const>
                 <Var>item</Var>
               </args>
             </Atom>
           </then>
         </Implies>
       </formula>
     </Forall>
    </sentence>
   </Group>
  </payload>
 </Document>

One of the Presentation Syntaxes

Document(
  Prefix(ppl  <http://example.com/people#>)
  Prefix(cpt  <http://example.com/concepts#>)
  Prefix(dc   <http://purl.org/dc/terms/>)
  Prefix(rif  <http://www.w3.org/2007/rif#>)
  Prefix(func <http://www.w3.org/2007/rif-builtin-function#>)
  Prefix(pred <http://www.w3.org/2007/rif-builtin-predicate#>)
  Prefix(xs   <http://www.w3.org/2001/XMLSchema#>)
  
  (* "http://sample.org"^^rif:iri _:pd[dc:publisher -> "http://www.w3.org/"^^rif:iri
                                      dc:date -> "2008-04-04"^^xs:date] *)
  Group
  (
    Forall ?item ?deliverydate ?scheduledate ?diffduration ?diffdays (
        cpt:reject(ppl:John ?item) :-
            And(cpt:perishable(?item)
                cpt:delivered(?item ?deliverydate ppl:John)
                cpt:scheduled(?item ?scheduledate)
                ?diffduration = External(func:subtract-dateTimes(?deliverydate ?scheduledate))
                ?diffdays = External(func:days-from-duration(?diffduration))
                External(pred:numeric-greater-than(?diffdays 10)))
    )
 
    Forall ?item (
        cpt:reject(ppl:Fred ?item) :- cpt:unsolicited(?item)
    )
  )
)

Other Presentation Syntaxes

Nothing standard... room for experimentation

Prefix ppl <http://example.com/people#>
Prefix cpt  <http://example.com/concepts#>
Prefix dc   <http://purl.org/dc/terms/>
Prefix rif  <http://www.w3.org/2007/rif#>
Prefix func <http://www.w3.org/2007/rif-builtin-function#>
Prefix pred <http://www.w3.org/2007/rif-builtin-predicate#>
Prefix xs   <http://www.w3.org/2001/XMLSchema#>
  
(* <http://sample.org> { _:pd dc:publisher lt;http://www.w3.org/>;
                                dc:date "2008-04-04"^^xs:date] } *)
if cpt:perishable(?item) and
   cpt:delivered(?item ?deliverydate ppl:John) and
   cpt:scheduled(?item ?scheduledate) and
   func:days-from-duration(?deliverydate - ?scheduledate) > 10
then cpt:reject(ppl:John ?item).

if   cpt:unsolicited(?item)
then cpt:reject(ppl:Fred ?item).

Slippery slope to "real" rule languages.

A Family of Dialects

But...

Not all engines implement the same features

Some features (retract and negation) are incompatible

Forward chaining, Backward chaining

So...

Core: common subset

BLD: (basic logic dialect) common subset of Prolog-style languages

PRD: (production rule dialect) common subset of Production Rule languages

Rule Language Features

Rule Language Features - BLD

Rule Language Features - PRD

Rule Language Features - Core

What if my feature is missing?

Double-check the specs

Check mailing list, Wiki

• public-rif-dev@w3.org (public archives)

Check the Framework for Logic Dialects

• Use as a menu of features
• Already has negations, aggregates, etc
• Can't all be used together
• Implementation may be difficult

Okay to define your own dialects

Extensions: Interoperability

When adding an extension, consider:

What should non-implementing systems do?

(controlling this is "extensibility")

Extending the Syntax

Add XML Elements, in your own namespace

Non-implementing systems will reject document

Document it, share on public-rif-dev@w3.org

Possible Fallback Mechanism

Ideally, non-implementing systems could look up extension

Syntactic sugar -> perfect rewrites

Other rewrites have some "impact"

Proposed as XTAN, but not adopted in RIF

RIF Summary

• Developed by diverse community over several years
• Stable XML format; evolving presentation syntaxes
• Three Stable Dialects; evolving set of extensions

Useful, yes. But "necessary"?

Use Case: Ad Hoc Reasoning

        if { ?p rdfs:range ?c.   
             ?x ?p ?y }
        then
           { ?y rdf:type ?c }
        

See OWL 2 RL in RIF

Use Case: Vocabulary Migration

In the January 2010 version, FOAF changed foaf:family_name to foaf:familyName. How many apps did this break?

Let's use this rule:

      if   { ?person foaf:family_name ?fam }
      then { ?person foaf:familyName ?fam }

• Put this rule at http://xmlns.com/foaf/0.1/family_name for forward chainers, crawlers
• Put this rule at http://xmlns.com/foaf/0.1/famileName for backward chainers, query systems
• Encourage all data consumers to do RIF inference

Then: migration becomes possible

(Yes, you could also do this with owl:equivalentProperty.)

Use Case: Scalable Data Integration 1

FOAF has both firstName + lastName and (combined) name. Many data sources do not provide both. (Vocabulary Mapping)

        if { ?person foaf:firstName ?first;
                     foaf:lastName ?last }
        then
           { ?person foaf:name func:string-join(?first " " ?last) }


	# Works for Hillary Rodham Clinton, not Sarah Jessica Parker
        if { ?person foaf:name ?name } and pred:contains(?name, " ")
        then
           { ?x foaf:firstName func:string-before(?name, " ");
                foaf:lastName func:string-after(?name, " ")
           }

• Do this within FOAF
• ...and between FOAF and vCard

Allows new vocabs to be deployed

Use Case: Scalable Data Integration 2

Facebook's Open Graph Protocol uses a simple-to-use (page-style) RDF vocabulary:

og:type - The type of your object, e.g., "movie". Depending on the type you specify, other properties may also be required.

That is:

   <http://www.imdb.com/title/tt0117500/> og:type "movie".

Is an IMDB web page a movie??

Convert to standard RDF modeling:

   if   { ?page og:type "movie";
                foaf:primaryTopic ?resource }
   then { ?resource rdf:type dbpedia-owl:Film }

These rules should be reachable Linked Data.

Motivation Summary

RIF for Linked Data Allows:

• Renaming of terms
• Migration in modeling
• Simultaneous use of multiple models
• ... without coordination or agreement

Web-Scale Data Integration

What Now?

RIF is stable, widely reviewed

Many implementation (not many products yet)

Use for Linked Data is experimental, but critical.

Test Suite:

• http://www.w3.org/2005/rules/wiki/Category:Test_Case
• http://www.w3.org/2005/rules/test/repository/
• Currently: 78 Approved

The Future:

• Products
• New Extensions, Dialects
• Look for deployment with Linked Data