A year on the Semantic Web @ W3C

A year on the Semantic Web @ W3C(or: what is happening these days?)Semantic Web Meetup, Seattle, 2010-06-17Ivan Herman, W3C

The Past…Some technologies have been recently finalized:OWL 2Rule Interchange Format (RIF)

The present…Technical work is going onSPARQL 1.1RDFa 1.1RDB2RDF“Community” contacts at W3C are also happening withhealth care and life science communityfinancial world, eg, XBRL(digital) library worldeGovernment

The (possible) futureFinalize the presentPossible new technical activities:ProvenanceRevision of RDF…

OWL 2A small revision of the 2004 version of OWLSome new features:keysextended datatypes facilitieseg, numerical intervals without relying on XML Schemasproperty chainsthe “uncle” example can now be formulated in OWLqualified cardinality restrictionsprofiles…Better documents, clearer structures

It was a slightly stormy process…There were misunderstanding between the “core” RDF and the OWL communities“does OWL abandon RDF?”will there be an OWL 2 Full specification at all?Luckily, all those were really just misunderstandings

The overall structure has not changedRDF/XMLmappingOWL/XMLFunc. Syntaxontology structureRDF graphmappingTurtleM‘ter syntaxOWL Ontologysyntaxsemanticscorrespondence theorem(for DL subset)Direct SemanticsRDF Based Semantics

OWL 2 profilesOWL 2 maintains the OWL Full and OWL DL “duality”But OWL Lite has been replaced by “profiles”:syntactic restrictions to OWLrestricted facilities  better reasoning performanceGoal is to make lighter OWL reasoners possible

OWL profilesOWL FullOWL DLOWL RLOWL ELOWL QL

An example: OWL RLGoal: to be implementable through rule enginesUsage follows a similar approach to RDFS: merge the ontology and the instance data into an RDF graph use the rule engine to add new triples (as long as it is possible) then, for example, use SPARQL to query the resulting (expanded) graphThis application model is very important for RDF based applications

What can be done in OWL RL?Many features are available:identity of classes, instances, propertiessubproperties, subclasses, domains, rangesunion and intersection of classes (though with some restrictions)property characterizations (functional, symmetric, etc)property chainskeyssome property restrictions (but not all inferences are possible)

What cannot be done in OWL RL?Some features are not available or are restricted:not all datatypes are availableno datatype restrictionsno minimum or exact cardinality restrictionsmaximum cardinality only with 0 and 1some consequences cannot be drawnVery informally: rules cannot draw conclusions that involves a “there is a resource such as…”

Why rules on the Semantic Web?Some conditions may be complicated in ontologies (ie, OWL)eg, Horn rules: (P1 & P2 & …) -> CIn many cases applications just want 2-3 rules to complete integrationIe, rules may be an alternative to (OWL based) ontologies

Things you may want to expressAn example from a bookshop integration:“I buy a novel with over 500 pages if it costs less than $20”something like (in an ad-hoc syntax):{ ?x rdf:type p:Novel; p:page_number ?n; p:price [ p:currency p:$; rdf:value ?z ].?n > "500"^^xsd:integer. ?z < "20.0"^^xsd:double. }=> { <me> p:buys ?x }

Things you may want to expressp:Novelrdf:type?np:page_number?n>500p:buys?x?xmep:pricep:$p:currencyrdf:value?z?z<20

RIF (Rule Interchange Format)The goals of the RIF:define simple rule language(s) for the Semantic Webdefine interchange formats for rule based systemsRIF defines several “dialects” of languagessome are geared towards production rule systems, for exampleie, RIF is not bound to RDF onlyIe, RIF is also a general framework to define/interchange rule languages

RIF CoreThe simplest RIF “dialect”A Core document issome directives like import, prefix settings for URIs, etca sequence of logical implicationstechnically, Horn rules without functionscan use the familiar datatypes and operatorshas the notion of “anonymous” resources, a bit like blank nodes

RIF SyntaxesRIF definesa “presentation syntax”a bit like the functional syntax for OWLa standard XML syntax to encode and exchange the rulesthere is a draft for expressing Core in RDFjust like OWL is represented in RDF

Remember the what we wanted from Rules?{ ?x rdf:type p:Novel; p:page_number ?n; p:price [ p:currency p:$; rdf:value ?z ]. ?n > "500"^^xsd:integer. ?z < "20.0"^^xsd:double. }=> { <me> p:buys ?x }

The same with RIF Presentation syntaxDocument ( Prefix … Group ( Forall ?x ?n ?z ( <me>[p:buys->?x] :- And( ?x rdf:type p:Novel ?x[p:page_number->?n p:price->_abc] _abc[p:currency->p:$ rdf:value->?z] External(pred:numeric-greater-than(?n "500"^^xsd:integer)) External(pred:numeric-less-than(?z "20.0"^^xsd:double)) ) ) ))

A word on the syntaxThe RIF Presentation syntax is… only syntaxIt can express more than what RDF needsHopefully, a syntax will emerge withclose to one of the RDF syntaxes with a better integration of rulescan be mapped on Core implementations

Usage of rule with RDFA system getsa set of RIF Core rules in some syntaxdata in RDFnew RDF triples are generatedSounds familiar? Remember OWL RL?

What about OWL RL?OWL RL stands for “Rule Language”…OWL RL is in the intersection of RIF Core and OWLinferences in OWL RL can be expressed with rulesthe rules are precisely described in the OWL spec, b.t.w.there are OWL RL implementations that are based on RIFAn application may also “declare” a subset of OWL RL rules it uses and let a RIF engine do the rest…

SPARQL as a unifying pointApplicationSPARQL ConstructSPARQL ConstructSPARQL EndpointSPARQL EndpointSPARQL ProcessorDatabaseTriple storeNLP TechniquesRDFaGRDDL, RDFaSQLRDFRDF GraphRelationalDatabaseHTMLUnstructured TextXML/XHTML

SPARQL 1.1: filling some missing featuresUpdate, ie, to change the RDF storeremove or add triplesNested queries (ie, SELECT within a WHERE clause)Negation (MINUS, and a NOT EXIST filter)Aggregate functions in SELECT (SUM, MIN, MAX…)Property path expressions (?xfoaf:knows+ ?y)Basic federated queriesCombination with entailment regimes (RDFS, OWL, RIF)

SPARQL 1.1 and RDFS/OWL/RIFSPARQL Engine with entailmentRDF DataQuery resultentailmentRDFS/OWL/RIF dataSPARQL PatternSPARQL PatternRDF Data with extra triplespattern matching

SPARQL 1.1 as a unifying pointApplicationSPARQL ConstructSPARQL ConstructSPARQL EndpointSPARQL EndpointSPARQL UpdateSPARQL UpdateSPARQL ProcessorDatabaseTriple storeOWL ReasoningNLP TechniquesRDFaGRDDL, RDFaSQLRDFRDF GraphRelationalDatabaseRIF ReasoningHTMLUnstructured TextXML/XHTML

RDFa has a significant tractionRDFa (and microformats) are indexed by Yahoo!, by Google,…Commercial, governmental, etc, sites add it to pages (BestBuy, Tesco, UK egov sites, LCS)Is used by Facebook’s Open Graph ProtocolMay turn into the largest source of RDF data on the Web…

RDFa 1.1A new Working Group on a new release of RDFaGoalssimplify the work of RDFa authors via new featuresseparation of RDFa “Core”, that can be used with any XML dialect, and XHTML+RDFa and HTML5+RDFadefinition of a separate RDFa APIIt is still at the beginning, first public drafts have just been published

“RDF Next Steps” WorkshopWorkshop takes place in Stanford in a weekThere were over 30 submissionsIssues:do we need a revision of RDF?if yes, what would that entail?Discussions will happen at the WorkshopA new Working Group might be created in 2010

Preliminary conclusions from the submissionsThere is probably no need for a radical overhaul of RDFSome new features/changes may become necessary

Some of the discussion topicsFeature changes:deprecation (reification, containers)new featuresnamed graphs, quads, n-quadslists as first class entitiesSemantic changes:change bnode semanticsadopt “ter Horst” semantics for RDFSremove current restrictions (literal subjects, bnode predicates)

Some of the discussion topicsSyntaxes:standard Turtle syntaxJsonnew (schema friendly) XML syntaxAtomSpecial vocabularies:unordered lists, measurement unitsn-ary relations, identity management

These are all discussion topics!Only future can tell what the community will agree upon in a charter (or charters)RDF is the basis for many things, any change must be carefully considered from a deployment point of view!

That is all I have time for…There are many issues that were not discussedprovenance, linked data, open government initiatives, applications, open R&D issues, …There is work for everyone!Think of convincing your employer to join W3C…… and then join one of the current or upcoming groups!

Thank you for your attention!These slides are also available on the Web: http://www.w3.org/2010/Talks/0617-Seattle-IH/

A year on the Semantic Web @ W3C

More Related Content

What's hot (20)

Viewers also liked (10)

Similar to A year on the Semantic Web @ W3C (20)

More from Ivan Herman (20)

Recently uploaded (20)

A year on the Semantic Web @ W3C

Editor's Notes