Semantic Web Service Discovery

This chapter surveys existing approaches to Semantic Web service discovery. Such semantic discovery will probably substitute existing keyword-based solutions in the near future, in order to overcome the limitations of the latter. First, the architectural components along with potential deployment scenarios are discussed. Subsequently, a wide range of algorithms and tools that have been proposed for the realization of Semantic Web service discovery are presented. Moreover, key challenges and open issues, not addressed by current systems, are identified. The purpose of this chapter is to update the reader on the current progress in this area of the distributed systems domain and to provide the required background knowledge and stimuli for further research and experimentation in semantics-based service discovery.

Reasoning on the Semantic Web

We describe reasoning as the process needed for using logic. Efficiently performing this process is a prerequisite for using logic to present information in a declarative way and to construct models of reality. In particular we describe description logic and the owl ontology language and explain that in this case reasoning amounts to graph completion operations that can be performed by a computer program. We give an extended example, modeling a building with wireless routers and explain how such a model can help in determining the location of resources. We emphasize how different assumptions on the way routers and buildings work are formalized and made explicit in our logical modeling, and explain the sharp distinction between knowing some facts and knowing all facts (open vs. closed world assumption). This should be helpful when using ontologies in applications needing incomplete real world knowledge.

Service-Oriented Processes

The Business Process Execution Language for Web Services (BPEL) is an emerging standard for specifying the behaviour of Web services at different levels of details using business process modeling constructs. It represents a convergence between Web services and business process technology. This chapter introduces the main concepts and constructs of BPEL and illustrates them by means of a comprehensive example. In addition, the chapter reviews some perceived limitations of BPEL and discusses proposals to address these limitations. The chapter also considers the possibility of applying formal methods and Semantic Web technology to support the rigorous development of service-oriented processes using BPEL.

Editing Tools for Ontology Creation

This chapter gives an overview of some editing tools for ontology construction. At the present time, the development of a project like the one of building an ontology demands the use of a software tool. Therefore, it is given a synopsis of the tools that the authors consider more relevant. This way, if you are starting out on an ontology project, the first reaction is to find a suitable ontology editor. Furthermore, the authors hope that by reading this chapter, it will be possible to choose an editing tool for ontology construction according to the project goals. The tools have been described following a list of features. The authors believe that the following features are pertinent: collaborative ontology edition, versioning, graphical tree view, OWL editor and many others (see Appendix 2).

Semantic Web Service Discovery in the WSMO Framework

The Web service modeling ontology (WSMO) provides a conceptual framework for semantically describing Web services and their specific properties. In this chapter we discuss how WSMO can be applied for service discovery. We provide a proper conceptual grounding by strictly distinguishing between service and Web service discovery and then present different techniques for realizing Web service discovery. In order to cover the complete range of scenarios that can appear in practical applications, several approaches to achieve the automation of Web service discovery are presented and discussed. They require different levels of semantics in the description of Web services and requests, and have different complexity and precision.

Semantic Search Engines Based on Data Integration Systems

As the use of the World Wide Web has become increasingly widespread, the business of commercial search engines has become a vital and lucrative part of the Web. Search engines are common place tools for virtually every user of the Internet; and companies, such as Google and Yahoo!, have become household names. Semantic search engines try to augment and improve traditional Web Search Engines by using not just words, but concepts and logical relationships. In this chapter a relevant class of semantic search engines, based on a peer-to-peer, data integration mediator-based architecture is described. The architectural and functional features are presented with respect to two projects, SEWASIE and WISDOM, involving the authors. The methodology to create a two level ontology and query processing in the SEWASIE project are fully described.

Semantic Web Services

The promise of dynamic selection and automatic integration of software components written to Web services standards is yet to be realized. This is partially attributable to the lack of semantics in the current Web service standards. To address this, the Semantic Web community has introduced semantic Web services. By encoding the requirements and capabilities of Web services in an unambiguous and machine-interpretable form, semantics make the automatic discovery, composition and integration of software components possible. This chapter introduces Semantic Web services as a means to achieve this vision. It presents an overview of Semantic Web services, their representation mechanisms, related work and use cases.

Introduction to Web Services

This chapter introduces the theory and design principles behind Web Service technology. It explains the models, specifications, and uses of this technology as a means to allow heterogeneous systems to work together to achieve a task. Furthermore, the authors hope that this chapter will provide sufficient background information along with information about current areas of research in the area of Web Services that readers will come away with an understanding of how this technology works and ways that it could be implemented and used.

The Process of Semantic Annotation of Web Services

Web services are software components that are—in general—distributed over multiple organizations. They provide functionality without showing implementation details for the purpose of abstracting from implementation as well as for the purpose of hiding private, that is, organization-internal, processes. Nevertheless, to use a Web service one must know some of its details, that is, what it does, what it requires, what it assumes, what it achieves, and to some extent, how it achieves its purpose. The different Web service standards, frequently summarized as WS*, allow Web services to be specified with descriptions of such details. In this chapter, we argue that one should go beyond WS* and that it is preferable to provide semantic descriptions, that is, specifications that can be understood and correctly interpreted by machines. Thereby, the particular focus of this contribution lies in analyzing the process of semantic annotation, that is, the process of deriving semantic descriptions from lower level specifications, implementations and contextual descriptions. Hence, the concern of this chapter is really orthogonal to most other work which equates Web service annotation with Web service specification. We illustrate here that this is not the case.

The Syntactic and the Semantic Web

This chapter gives an overview of the evolution of the Web. Initially, Web pages were intended only for human consumption and were usually displayed on a Web browser. New Internet business models, such as B2B and B2C, required organizations to search for solutions to enable a deep interoperability and integration between their systems and applications. One emergent solution was to define the information on the Web using semantics and ontologies in a way that it could be used by computers not only for display purposes, but also for interoperability and integration. The research community developed standards to semantically describe Web information such as the resource description framework and the Web Ontology Language. Ontologies can assist in communication between human beings, achieve interoperability among software systems, and improve the design and the quality of software systems. These evolving Semantic Web technologies are already being used to build semantic Web based systems such as semantic Web services, semantic integration of tourism information sources, and semantic digital libraries to the development of bioinformatics ontologies.