The WSMO / L / X Approach Michael Stollberg DERI – Digital Enterprise Research Institute Alternative Frameworks for Semantics in Web Services: Possibilities for Inclusion in Future Standards SDWP 2005 workshop held at the ICWS 2005, Orlando, Florida, 2005 July 11

2 SDWP 2005 panel, Orlando, Florida (USA), July 2005 WSMO Working Groups A Conceptual Model for SWS A Formal Language for WSMO A Rule-based Language for SWS Execution Environment for WSMO W3C Member Submission

3 SDWP 2005 panel, Orlando, Florida (USA), July 2005 Aims & Approach Semantic Web Services as integrated technology for realizing the vision of the Semantic Web –Current WS technology stack (SOAP, WSDL, UDDI) failed realizing the “Web Service promise” –Ontologies + Semantic Descriptions for automated Web Service Usage WSMO / L / X = fully fletched framework for Semantic Web Services –Meta-level ontology for semantically describing core elements of Semantic Web Services (WSMO) –well-layered semantic description langauge (WSML) –SWS technologies for automated discovery, composition, conversation, execution –SWS Execution Environment WSMX

4 SDWP 2005 panel, Orlando, Florida (USA), July 2005 Semantic Web Service Technology Publication: create and publish semantic descriptions Discovery: detect Web Service capable of resolving a given tasks Selection: choose most appropriate among available Web Services Composition: combine services for more complex functionality Mediation: resolve mismatches (data, protocol, process) between resources that shall interoperate Execution Support: automated invocation –Monitoring: control the execution process –Compensation: provide transactional support and undo or mitigate unwanted effects –Replacement: facilitate the substitution of services by equivalent ones –Auditing: verify that service execution occurred in the expected way Aim: automated technologies

5 SDWP 2005 panel, Orlando, Florida (USA), July 2005 WSMO Top Level Notions Objectives that a client wants to achieve by using Web Services Provide the formally specified terminology of the information used by all other components Semantic description of Web Services: - Capability (functional) - Interfaces (usage) Connectors between components with mediation facilities for handling heterogeneities Core Elements for Semantic Web Services

6 SDWP 2005 panel, Orlando, Florida (USA), July 2005 WSMO Web Service Description Web Service Implementation (not of interest in Web Service Description) Choreography --- Service Interfaces --- Capability functional description WS - Advertising of Web Service - Support for WS Discovery client-service interaction interface for consuming WS - External Visible Behavior - Communication Structure - ‘Grounding’ realization of functionality by aggregating other Web Services - functional decomposition - WS composition Non-functional Properties DC + QoS + Version + financial - complete item description - quality aspects - economic aspects - for item management WS Orchestration

7 SDWP 2005 panel, Orlando, Florida (USA), July 2005 OWL and WSML reasoning facilities from DL & LP world needed WSML as well-layered Semantic Web Language OWL Lite OWL DL OWL Full WSML Flight WSML DL WSML Core WSML Rule WSML Full full RDF(S) support subset Description Logics Logic Programming First Order Logic

8 SDWP 2005 panel, Orlando, Florida (USA), July 2005 WSMO Service Interface Description Model common formal model for Service Interface description –ontologies as data model –based on ASMs –not restricted to any executable communication technology general structure: –Vocabulary Ω: ontology schema(s) used in service interface description usage for information interchange: in, out, shared, controlled –States ω(Ω): a stable status in the information space defined by attribute values of ontology instances –Guarded Transition GT(ω): state transition general structure: if (condition) then (action) different for Choreography and Orchestration additional constructs: add, delete, update

9 SDWP 2005 panel, Orlando, Florida (USA), July 2005 WSMX Usage Scenario - P2P

10 SDWP 2005 panel, Orlando, Florida (USA), July 2005 WSMX Architecture

11 SDWP 2005 panel, Orlando, Florida (USA), July 2005 Position Semantic Web vision / Web Service promise not reachable without semantics –WSMO / L / X as full semantically enabled Web Service techology –demonstration of benefits / added value of semantic technology Semantic descriptions are complicated to create –Ontology / Knowledge Engineers needed –exhaustive tool support needed for description / implementation creation (“hide semantics from system developers”) What future standards should contain: –meta-level description structure of SWS core elements (what is described) –semantic description langauge (how it is described) –not restricted to specific technology or implementation design