WWW: WSMO, WSML, and WSMX in a Nutshell Dumitru Roman 1, Jos de Bruijn 1, Adrian Mocan 1, Holger Lausen 1,2, John Domingue 3, Christoph Bussler 2, and Dieter Fensel 1,2 1 Digital Enterprise Research Institute, Innsbruck, Austria 2 Digital Enterprise Research Institute, Galway, Ireland 3 Knowledge Media Institute, the Open University, UK Proceedings of the first Asian Semantic Web Conference (ASWC 2006), Beijing, China, September 3-7, 2006 Advisor : 張欽智 Presenter : 許邑丞

2007/08/28 Kotin Hsu 2 OUTLINE Introduction Introduction Web Service Modeling Ontology (WSMO) Web Service Modeling Ontology (WSMO) Web Service Modeling Language (WSML) Web Service Modeling Language (WSML) Web Service Execution Environment (WSMX) Web Service Execution Environment (WSMX) Conclusions Conclusions

2007/08/28 Kotin Hsu 3 Introduction Web Services ? Web Services ? Pieces of functionalities which are accessible over the Web Towards seamless integration of distributed software components using Web standards Current Web Service Technologies SOAP, WSDL, UDDI Syntactic Level Still require human interaction

2007/08/28 Kotin Hsu 4 Introduction (Cont.) Semantic Web Services (SWS) Semantic Web Services (SWS) Usage of ontologies as the basis of such semantic descriptionUsage of ontologies as the basis of such semantic description In order to provide the basis for SWS, requires three functional layers In order to provide the basis for SWS, requires three functional layers A Foundational conceptual modelA Foundational conceptual model A formal language to provide formal syntax an semanticsA formal language to provide formal syntax an semantics An Execution EnvironmentAn Execution Environment

2007/08/28 Kotin Hsu 5 Introduction (Cont.) Overivew of such a framework Overivew of such a framework Web Service Modeling Ontology (WSMO)Web Service Modeling Ontology (WSMO) Provides a general overview of an ontology for SWS Provides a general overview of an ontology for SWS Web Service Modeling Language (WSML)Web Service Modeling Language (WSML) Provides a formal syntax and semantics for WSMO Provides a formal syntax and semantics for WSMO Web Service Modeling Environment (WSMX)Web Service Modeling Environment (WSMX) Implementation for WSMO, offering support for interacting with SWS Implementation for WSMO, offering support for interacting with SWS

2007/08/28 Kotin Hsu 6 Web Service Modeling Ontology (WSMO) WSMO WSMO Provides a conceptual model for structuring the semantic annotation of services; it defines ontological specifications for the core elements of SWS

2007/08/28 Kotin Hsu 7 WSMO Design Principles WSMO Design Principles WSMO Design Principles Web Compliance : Uses Web technologies Ontology-Based : Uses ontologies as data model Strict Decoupling : Elements are defined independently from each Others Centrality of Mediation : Handling of heterogeneities that naturally arise in open environments Ontological Role Separation : distinction between the desires of users or clients and available services

2007/08/28 Kotin Hsu 8 WSMO Design Principles WSMO Design Principles WSMO Design Principles Description versus Implementation : differentiation between the descriptions of SWS elements and executable technologies Execution Semantics : formal execution semantics of reference implementations Service versus Web service : differentiation between Web services as a computational entity which is able to achieve a users goal, and services as the actual value provided Web services

2007/08/28 Kotin Hsu 9 WSMO Ontology Elements WSMO ontology elements WSMO ontology elements Defined in a meta-meta-model language base on Meta Object Facility (MOF)Defined in a meta-meta-model language base on Meta Object Facility (MOF) Meta-meta-model Layer  The Language defining WSMOMeta-meta-model Layer  The Language defining WSMO Meta-model Layer  WSMO itselfMeta-model Layer  WSMO itself Model Layer  Actual ontologies,Web Services,goals,mediatorsModel Layer  Actual ontologies,Web Services,goals,mediators Information Layer  Actual dataInformation Layer  Actual data

2007/08/28 Kotin Hsu 10 WSMO Element Properties WSMO Element Properties : WSMO Element Properties : GoalsGoals provide means to characterize user requests in terms of functional and non-functional requirements Web Service DescriptionsWeb Service Descriptions Choreography An Interface definition that defines access patterns of a service Orchestration Means to express services as being composed from others services

2007/08/28 Kotin Hsu 11 WSMO Element Properties WSMO Element Properties : WSMO Element Properties : OntologiesOntologies provide a first and important means to achieve interoperability between goals and services as well as between various services themselves MediatorsMediators provide additional procedural elements to specify further mappings that cannot directly be captured through the usage of ontologies

2007/08/28 Kotin Hsu 12 Four Types of Mediators WSMO defines four types of mediators for connecting WSMO elements OO Mediators : connect and mediate heterogeneous ontologies GG Mediators : connect Goals WG Mediators : link Web services to Goals WW Mediators : connect interoperating Web services

2007/08/28 Kotin Hsu 13 Web Service Modeling Language (WSML) A language for the specification of different aspects of SWS; it takes into account all aspects identified by WSMO

2007/08/28 Kotin Hsu 14 Web Service Modeling Language (WSML) Variants of WSML : Variants of WSML : WSML-CoreWSML-Core Based on Description Logic and Horn Logic Based on Description Logic and Horn Logic It has the Least expressive power of all the WSML variants It has the Least expressive power of all the WSML variants Main Features : concepts, attributes, binary relations and instances, concept, relation hierarchies and datatype Main Features : concepts, attributes, binary relations and instances, concept, relation hierarchies and datatype

2007/08/28 Kotin Hsu 15 Web Service Modeling Language (WSML) Variants of WSML : Variants of WSML : WSML-DLWSML-DL Captures the Description Logic, which is major part of the OWL Captures the Description Logic, which is major part of the OWL WSML-FlightWSML-Flight An extension of WSML-Core which provides a powerful rule language Adds Features : meta-modeling, constraints, nonmonotonic negation

2007/08/28 Kotin Hsu 16 Web Service Modeling Language (WSML) Variants of WSML : Variants of WSML : WSML-RuleWSML-Rule Extends WSML-Flight with feature from Logic Programming Extends WSML-Flight with feature from Logic Programming Function symbols, unsafe rules, unstratified negation under the Well-Founded semantics Function symbols, unsafe rules, unstratified negation under the Well-Founded semantics WSML-FullWSML-Full Unifies WSML-DL and WSML-Rule under a First-Order umbrella with extensions to support the nonmonotonic negation of WSML-Rule

2007/08/28 Kotin Hsu 17 Web Service Execution Environment (WSMX) WSMX WSMX An execution environment which enables discovery, selection, mediation, composition and invocation of SWS WSMX external behavior is described in terms of so-called entry points which represents standard interfaces that enable communication with external entities

2007/08/28 Kotin Hsu 18 WSMX Four Entry Points There are four mandatory entry points that have to be available in each working instance of the system : One-Way goal execution This entry point allows the realization of a goal without any back and forth interactions Web Service discovery A more complex (and realistic) scenario is to only consult WSMX about the set of Web services that satisfy a given goal

2007/08/28 Kotin Hsu 19 WSMX Four Entry Points Send messageSend message After the decision on which service to use was already made, a conversation involving back and forth messages between the requester and WSMX can start Store entity in the registryStore entity in the registry This entry point provide an interface for storing WSMO entities (described in WSML) in the repository

2007/08/28 Kotin Hsu 20 Conclusions Other Approaches for SWS Other Approaches for SWS OWL-SOWL-S SWSFSWSF IRS-IIIIRS-III WSDL-SWSDL-S WSMO provides The conceptual and technical means to realize SWS, Improving the cost-effectiveness, scalability and robustness of current solutions, WSML provides A formal syntax and semantics for WSMO by offering different variants based on different logics in order to provide different levels of logical expressiveness WSMX provides A reference implementation for WSMO and interoperation of SWS.