WSDL Mapping to RDF/Semantic Web

1
WSDL Mapping to RDF/Semantic Web

• July, 2004
• London, England F2F

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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

3
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
  RD

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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

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Modeling choices

• Model the component model in RDF OWL
• E.g., have a class wsdl-ontComponent and
  wsdl-ontProperty
• Then, relate Components to Properties via a
  predicate, i.e., contains
• Map the component model to RDF OWL
• Components are individuals, and properties are
  rdfProperties
• 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

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ExampletargetNamespace

• 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

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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)
• Erthis is the XML Schema working group, yes?

8
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?

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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

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Roundtripping

• Probably infeasible, if not impossible
• Cant roundtrip components to/from XML
• E.g., include/import information is lost
• Documentation has no component
• RDFOWL 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

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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 rdftype ValidCreditCard ?x hasLimit
  ?y ?y gt 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

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Some references

• OWL-S (1.1) http//www.daml.org/services/owl-s/1.
  1B/
• WS-Archt http//www.w3.org/2004/02/wsa/
• WSMO http//www.wsmo.org/
• SWSL http//www.daml.org/services/swsl/
• PSL http//www.mel.nist.gov/psl/
• WSDL-S http//lsdis.cs.uga.edu/lib/download/WSDL-
  S.doc
• Opt http//cs-www.cs.yale.edu/homes/dvm/papers/op
  t-manual.pdf
• OWL-S API http//www.mindswap.org/2004/owl-s/api/
  
• Task Computing http//tc.flacp.fujitsulabs.com/

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Cont targetNamespace

• May be able to infer equivalence (perhaps only in
  OWL Full)
• ltowlDatatypeProperty rdfidname/gt
• ltowlDatatypeProperty rdfidtargetNamespacegt
• ltowlObjectProperty rdfidqnamegt
• lt!--Snip axioms setting the range to a clas
  Qname which has exactly one name and
  targetNamespace--gt
• ltowlClass rdfidInterfacegt
• ltrdfssubClassOfgt
• ltowlRestrictiongt
• ltowlonProperty rdfresourceqname/gt
• ltowlcardinality rdfdatatypexsdnonNegative
  Integergt1lt/gt