Current industry standards for describing Web Services focus on ensuring interoperability across diverse platforms, but do not provide a good foundation for automating the use of Web Services. Representational techniques being developed for the Semantic Web can be used to augment these standards. The resulting Web Service specifications enable the development of software programs that can interpret descriptions of unfamiliar Web Services and then employ those services to satisfy user goals. OWL-S ("OWL for Services") is a set of notations for expressing such specifications, based on the Semantic Web ontology language OWL. It consists of three interrelated parts: a profile ontology, used to describe what the service does; a process ontology and corresponding presentation syntax, used to describe how the service is used; and a grounding ontology, used to describe how to interact with the service. OWL-S can be used to automate a variety of service-related activities involving service discovery, interoperation, and composition. A large body of research on OWL-S has led to the creation of many open-source tools for developing, reasoning about, and dynamically utilizing Web Services.

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Bringing Semantics to Web Services with OWL-S

Web services are a consolidated reality of the modern Web with tremendous, increasing impact on everyday computing tasks. They turned the Web into the largest, most accepted, and most vivid distributed computing platform ever. Yet, the use and integration of Web services into composite services or applications, which is a highly sensible and conceptually non-trivial task, is still not unleashing its full magnitude of power. A consolidated analysis framework that advances the fundamental understanding of Web service composition building blocks in terms of concepts, models, languages, productivity support techniques, and tools is required. This framework is necessary to enable effective exploration, understanding, assessing, comparing, and selecting service composition models, languages, techniques, platforms, and tools. This article establishes such a framework and reviews the state of the art in service composition from an unprecedented, holistic perspective.

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Web Service Composition: A Survey of Techniques and Tools

Current efforts in Semantic Web Services do not sufficiently address the industrial developments of SOA technology in regards to bottom-up modeling of services, that is, building incremental layers on top of existing service descriptions. An important step in this direction has been made in the W3C by the SAWSDL WG proposing a framework for annotating WSDL services with arbitrary semantic descriptions. We build on the SAWSDL layer and define WSMO-Lite service ontology, narrowing down the use of SAWSDL as an annotation mechanism for WSMO-Lite. Ultimately, our goal is to allow incremental steps on top of existing service descriptions, enhancing existing SOA capabilities with intelligent and automated integration.

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WSMO-lite annotations for web services

The easiness of managing and configuring resources and the low cost needed for setup and maintaining Cloud services have made Cloud Computing widespread. Several commercial vendors now offer solutions based on Cloud architectures. More and more providers offer new different services every month, following their customers needs. Anyway, it is very hard to find a single provider which offers all services needed by end users. Furthermore, different vendors propose different architectures for their Cloud systems and usually these are not compatible. Very few efforts have been done in order to propose a unified standard for Cloud Computing. This is a problem, since different Cloud systems and vendors have different ways to describe and invoke their services, to specify requirements and to communicate. Hence a way to provide a common access to Cloud services and to discover and use required services in Cloud federations is appealing. mOSAIC project addresses these problems by defining a common ontology and it aims at developing an open-source platform that enables applications to negotiate Cloud services as requested by users. The main problem in defining the mOSAIC ontology is in the heterogeneity of terms used by Clouds vendors, and in the number of standards which refer to Cloud Systems with different terminology. In this work the mOSAIC Cloud Ontology is described. It has been built by analysing Cloud standards and proposals. The Ontology has been then refined by introducing individuals from real Cloud systems.

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An analysis of mOSAIC ontology for Cloud resources annotation

Content delivery has undergone a sea of changes in recent years. While even only ten years back the major delivery channels were television and radio broadcast, nowadays content is delivered digitally via the Internet or other electronic delivery channels. The engineering problem of delivering multimedia content through the Internet has received much attention by the research community. However, the delivery of content to heterogeneous mobile terminals in a community context still poses many problems. Early Internet based content delivery systems were designed as centralized systems where content is provided from a central server to a large population of the end users (see Fig. 15.1-(a)). This trend is now shifting towards decentralized systems, such as Peer-to-Peer (P2P) systems, in which the role of the content provider and producer is no longer restricted to a few professional content creators. Thus, the content delivery paths is not anymore only from a central server through backbone networks to the end users, but also from one end user to other end user(s) (see Fig. 15.1-(b)). This has been triggered by the emergence of relatively cheap consumer electronics enabling everybody to become a content producer; and

Infrastructures for Community Networks

The current WSDL standard operates at the syntactic level and lacks the semantic expressivity needed to represent the requirements and capabilities of Web Services. Semantics can improve software reuse and discovery, significantly facilitate composition of Web services and enable integrating legacy applications as part of business process integration. The Web Service Semantics technical note defines a mechanism to associate semantic annotations with Web services that are described using Web Service Description Language (WSDL). It is conceptually based on, but a significant refinement in details of, the original WSDL-S proposal [WSDL-S] from the LSDIS laboratory at the University of Georgia. In this proposal, we assume that formal semantic models relevant to the services already exist. In our approach, these models are maintained outside of WSDL documents and are referenced from the WSDL document via WSDL extensibility elements. The type of semantic information that would be useful in describing a Web Service encompass the concepts defined by the semantic Web community in OWL-S [OWL-S] and other efforts [METEOR-S, WSMO]. The semantic information specified in this document includes definitions of the precondition, input, output and effects of Web service operations. This approach offers multiple advantages over OWL-S. First, users can describe, in an upwardly compatible way, both the semantics and operation level details in WSDLa language that the developer community is familiar with. Secondly, by externalizing the semantic domain models, we take an agnostic approach to ontology representation languages. This allows Web service developers to annotate their Web services with their choice of ontology language (such as UML or OWL) unlike in OWL-S. This is significant because the ability to reuse existing domain models expressed in modeling languages like UML can greatly alleviate the need to separately model semantics. Finally, it is relatively easy to update the existing tooling around WSDL specification to accommodate our incremental approach. Status This is a technical note provided for discussion purposes and to elicit feedback on approaches to adding semantics to Web services descriptions. Table of

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Joel Farrell

Papers

Web Service Semantics - WSDL-S