WSDL Mapping to RDF/Semantic Web July, 2004 London, England F2F

The requirement 4.11 Mapping to the Semantic Web –R070 The WG specification(s) MUST allow providing a mapping from the description language to [RDF]. (From the Charter. Last revised 11 April, 2002.) –Must allow? Ok, done

Semantic Web Description Languages Expressed in KR/logic based formalisms –OWL, F-Logic, General First Order Logic, Situation Calculus, PDDL –Thus, generally aim at supporting logical theories about the services Satisfiabily and entailment considered key Major current contenders –Heading for convergence: OWL-S (OWL and Sitcalc based) WSMO (F-Logic based) SWSL (Lots and lots and lots of things) –Others: various straw proposals, WSDL-S, WS-Arch ontologies Some industry uptake and interest –E.g., Fujistu moved end user research project to R&D

Language Choices Within W3C –RDF, RDFS, OWL Lite/DL vs. Full With momentum –F-Logic, SWRL, FLOWS (SWRL ++) Not all are largely compatible –Restrict to a subset of RDF/RDFS thats roughly common Not as useful, but much less work –Aim for a fuller ontology in OWL DL But have a dumb down strategy

Modeling choices Model the component model in RDF & OWL –E.g., have a class wsdl-ont:Component and wsdl- ont:Property –Then, relate Components to Properties via a predicate, i.e., contains Map the component model to RDF & OWL –Components are individuals, and properties are rdf:Properties –Gets away from the container metaphor Definiately not mapping the XML or Infoset –If anyone produces a complete mapping of the Infoset and Schema components, this comes free

Example:targetNamespace targetNamespace –The components directly defined within a single Definitions component are said to belong to the same target namespace. The target namespace therefore groups a set of related component definitions and represents an unambiguous name for the intended semantics of the collection of components. The target namespace URI SHOULD point to a human or machine processable document that directly or indirectly defines the intended semantics of those components. Some choices –targetNamespace URI designates the RDF/OWL document or ontology –targetNamespace URI names the Definitions individual –There must be a property targetNamespace on the Definitions (and on other things): Exclusively, or for redundancy May be able to infer various sorts of component equivalence

Another example: Types Simplest: use URIs to identify all visible, legal types –Use enumeration classes to constrain the values of, e.g., the element property –Unclear what happens if operation member of more than one interface in more than one definition –Essentially no embedding More complex: try to embed type/element/etc. definitions when possible Please no: create mapping of XML Schema –Little hope of interestingly preserving semantics Lack of r-transitive closure and well foundedness decisive? Could try to add such to OWL (prior work by Calavenese et al) Er…this is the XML Schema working group, yes?

Aligning with WS-Arch WS-Arch mentions operations, and defines operation in the glossary –But no top level concept in doc or ontology It has Action And Service task MEP seems right Do we/can we want to fix or just extend the WS-Arch ontologies?

Grounding OWL-S (among others, e.g., WSMO) ground processes in operations –Might seem backwards to some folks! Processes are executable (or executing) thingies –Could be software, could be a robot, could be a committee Processes generally have (worldly) effects Often used as planning operators –Fairly significant support in manufacturing (PSL) Beyond what WSDL says now –But pretty common way mappings are used –Providing supports would be useful and not hard

Roundtripping Probably infeasible, if not impossible –Cant roundtrip components to/from XML E.g., include/import information is lost Documentation has no component –RDF&OWL are fairly free Tolerate missing or merged information Can derive information implicit in the base –Including merges Expect lots of flat aggregation People will want to author and programmtically build WSDL from RDF –Not sure how far to go here with advice –Even selecting chunks of RDF to embed seems hard

Example: OWL-S PEs OWL-S 1.1 allows specs for preconditions and effects –Conjunctions of SWRL atoms (RDF triples with subject and object variables) –Associated with a process Thus, often with an operation –Used to express side constraints on engagement E.g., ?x rdf:type ValidCreditCard & ?x hasLimit ?y & ?y > $500 How to (generically) translate to WSDL? –Ideally want them grouped with operations –Require/encourage defining extentions with mappings? –Will include (some thing like this) as example appendix

Some references OWL-S (1.1): WS-Archt: WSMO: SWSL: PSL: WSDL-S: Opt: manual.pdfhttp://cs- manual.pdf OWL-S API: Task Computing:

Cont: targetNamespace May be able to infer equivalence (perhaps only in OWL Full) 1