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The Digital Enterprise Research Institute (DERI), a leading European research institute in the field of Semantic Web and Semantic Web services technology, has announced the submission of its Web Services Modeling Ontology (WSMO) to the World Wide Web Consortium (W3C). The multi-part submission package was made on April 04, 2005 by five institutions: DERI Innsbruck at the Leopold-Franzens-Universität Innsbruck, Austria; DERI Galway at the National University of Ireland, Galway, Ireland; British Telecom (BT, UK), The Open University (UK), and SAP AG (Germany).
The Web Service Modeling Ontology, according to DERI's announcement, "has been under development over the past two years within the WSMO working group. It provides a comprehensive framework for addressing Semantic Web services challenges and it is designed to help overcome the current problems of Enterprise Application Integration (EAI) and Service-Oriented Architectures (SOA). WSMO provides a conceptual framework and a formal language for semantically describing all relevant aspects of Web services in order to facilitate the automation of discovering, combining and invoking electronic services over the Web."
The Web Service Modeling Ontology Primer presented as part of the Member Submission describes the objective of WSMO as an attempt "to solve the application integration problem for Web services by defining a coherent technology for Semantic Web services. WSMO takes the Web Service Modeling Framework (WSMF) as starting point and further refines and extends its concepts. In order to achieve automated discovery, composition, and execution of Web services a conceptual model alone is insufficient. In addition, a formal language is required to write down annotations of Web services according to the conceptual model. Logical inference-mechanisms can be applied to the descriptions in this language. In order to allow appropriate, satisfactorily logic-based reasoning on Semantic Web services, the description language has to provide reasonable expressivity, together with well-defined formal semantics. The Web Service Modeling Language (WSML) is a family of languages which formalizes WSMO."
Three primary prose specifications are included in the WSMO Submission. The Web Services Modeling Ontology (WSMO) document provides ontological specifications for the core elements of Semantic Web services. This document "describes the overall structure of WSMO by its four main elements: ontologies, which provide the terminology used by other WSMO elements; Web service descriptions, which describe the functional and behavioral aspects of a Web service; goals that represent user desires; and mediators, which aim at automatically handling interoperability problems between different WSMO elements. Along with introducing the main elements of WSMO, the syntax of the formal logic language used in WSMO is provided."
The Web Service Modeling Language (WSML) document provides the language to formally describe all the elements defined in WSMO. It "introduces the Web Service Modeling Language WSML which provides a formal syntax and semantics for the Web Service Modeling Ontology WSMO. WSML is based on different logical formalisms, namely: Description Logics, First-Order Logic and Logic Programming, which are useful for the modeling of Semantic Web services. WSML consists of a number of variants based on these different logical formalisms, namely WSML-Core, WSML-DL, WSML-Flight, WSML-Rule and WSML-Full. WSML-Core corresponds with the intersection of Description Logic and Horn Logic. The other WSML variants provide increasing expressiveness in the direction of Description Logics and Logic Programming. Finally, both paradigms are unified in WSML-Full, the most expressive WSML variant."
WSML "is specified in terms of a normative human-readable syntax. Besides the human-readable syntax, WSML has an XML and an RDF syntax for exchange over the Web and for interoperation with RDF-based applications. Furthermore, we provide a mapping between WSML ontologies and OWL ontologies for interoperation with OWL ontologies through a common semantic subset of OWL and WSML."
The Web Service Execution Environment (WSMX) document included in the submission describes "an execution environment that enables discovery, selection, mediation, invocation and interoperation of Semantic Web Services and provides a reference implementation of WSMO. The development process for WSMX includes defining its conceptual model (i.e. WSMO), modeling its execution semantics (implemented by a dynamic execution semantic engine capable of interpreting any formal definition of system behaviour provided by third parties) and designing the WSMX system architecture. For the initial version of WSMX a complete architecture including discovery, mediation, selection and invocation components has been designed including all required supporting components enabling exchange of messages between the requesters and the providers of services."
A 'Resource Manager' dederibed in WSMX is responsible for the management of the repositories that store definitions of any WSMO entity (Web services, goals, ontologies and mediators) and non-WSMO related objects in WSMX. Currently WSMX provides five repositories: Web Service Repository, Goal Repository, Ontology Repository, Mediator Repository and Data Repository. This document also recognizes that ebXML and UDDI repositories can be used for WSMX data persistence."
The WSMO Member Submission suggests that W3C consider the technology as "an input for work in a new Semantic Web Services Description Working Group at W3C. Although WSMO "has been developed and deployed in collaboration with a number of industrial partners and research groups making up the WSMO working group, further enhancements are planned in the light of feedback from the W3C, knowledge and insights from real world case studies, and from ongoing work in related research projects and networks of excellence."
W3C has acknowledged receipt of the WSMO Member Submission but has not yet allocated any resources to the issues addressed by it. The W3C Team Comment on Web Service Modeling Ontology (WSMO) Submission by Carine Bournez notes that the overall design, which "relies on a simple Class/Sub-Class/Attributes/Types of attributes data model, is not based on W3C recommendations in the Semantic Web area, such as OWL and RDF. The notion of choreography in WSMO is obviously very far from the definition and scope presented in WS-CDL, and there is also no connection to any description language at lower level, like WSDL." Therefore, W3C "would like to see more background for the whole piece of work, by means of real use cases for example, to describe the problems that this framework is trying to solve."
