nach oben

2008 | Buch

Kapitel lesen Erstes Kapitel lesen

The Semantic Web

Semantics for Data and Services on the Web

verfasst von: Vipul Kashyap, Christoph Bussler, Matthew Moran

Verlag: Springer Berlin Heidelberg

Buchreihe : Data-Centric Systems and Applications

Enthalten in: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik" , Springer Professional "Wirtschaft"

Einloggen, um Zugang zu erhalten

Über dieses Buch

A decade ago Tim Berners-Lee proposed an extraordinary vision: despite the p- nomenal success of the Web, it would not, and could not, reach its full potential unless it became a place where automated processes could participate as well as people. This meant the publication of documents and data to the web in such a way that they could be interpreted, integrated, aggregated and queried to reveal new connections and answer questions, rather than just browsed and searched. Many scoffed at this idea, interpreting the early emphasis on language design and reas- ing as AI in new clothes. This missed the point. The Grand Challenge of the Semantic Web is one that needs not only the information structure of ontologies, metadata, and data, but also the computational infrastructure of Web Services, P2P and Grid distributed computing and workflows. Consequently, it is a truly who- system and multi-disciplinary effort. This is also an initiative that has to be put into practice. That means a pragmatic approach to standards, tools, mechanisms and methodologies, and real, challenging examples. It would seem self-evident that the Semantic Web should be able to make a major contribution to clinical information discovery. Scientific commu- ties are ideal incubators: knowledge-driven, fragmented, diverse, a range of str- tured and unstructured resources with many disconnected suppliers and consumers of knowledge. Moreover, the clinicians and biosciences have embraced the notions of annotation and classification using ontologies for centuries, and have dema- ing requirements for trust, security, fidelity and expressivity.

Inhaltsverzeichnis

Frontmatter

Preliminaries

Frontmatter

1. Introduction

Semantics in the Webster dictionary is defined as meaning or relationship of meanings of a sign or a set of signs [4]. From an Information Systems perspective, semantics of information can be defined as the meaning and use of information [1]. The Semantic Web is defined as an extension of the current Web in which information is given a well-defined meaning, better enabling people and computers to work together [2]. The Semantic Web is a vision: the idea of having data on the Web defined and linked in a way that it can be used by machines not just for display purposes, but also for automation, integration and reuse of data across various applications. The goal of the Semantic Web initiative is as broad as that of the Web: to create a universal medium for the exchange of data. It is envisaged to smoothly interconnect personal information management, enterprise application integration, and the global sharing of commercial, scientific and cultural data.

2. Use Case and Functional Requirements

The success of new innovations and technologies are very often disruptive in nature. At the same time, they enable novel next-generation infrastructures and solutions. These solutions often give rise to creation of new markets and/or introduce great efficiencies. For example, the standardization and deployment of IP networks resulted in introducing novel applications that were not possible in older telecom networks. The Web itself has revolutionized the way people look for information and corporations do business. Web-based solutions have dramatically driven down operational costs both within and across enterprises. The Semantic Web is being proposed as the next-generation infrastructure, which builds on the current Web and attempts to give information on the Web a well-defined meaning [2]. This may well be viewed as the next wave of innovation being witnessed in the information technology sector.

Information Aspects of the Semantic Web

Frontmatter

3. Semantic Web Content

In this chapter, we begin with an understanding of the nature of data and content available on the web today and discuss preliminary approaches for representing metadata. We will then methodically enumerate and discuss various types of Semantic Web content spanning structured, unstructured and semi-structured data, with examples from the healthcare and life science domains. The basic premise of the Semantic Web is to build up on the current web to give each piece of data a well-defined meaning. We will illustrate with examples the notion of “self-describing” data and the role of metadata descriptions and ontologies in achieving this goal.

4. Metadata Frameworks

We present a discussion of various frameworks and schemes proposed for representation, storage and manipulation of data and metadata. Standards and specifications proposed by the World Wide Web Consortium (W3C) such the eXtensible Markup Language (XML) [43], Resource Description Framework (RDF) [42] and the Web Ontology Language (OWL) [45] are presented. The frameworks are described and contrasted along various dimensions such as the data model and expressiveness of the specification and query languages for manipulation of metadata specifications and repositories. We will also discuss relationships of these metadata frameworks with rule-based and ontology standards, where applicable.

5. Ontologies and Schemas

We present a discussion of various ontology and schema-like artifacts used in various fields of activity such as library sciences, relational databases, knowledge representation and medical informatics. We then discuss languages proposed for representation of ontologies and schemas such as XML Schema [87], RDF Schema [88] and OWL [54] and present a comparative evaluation of these languages. The model-theoretic semantics underlying constructs in RDF Schema and OWL are also presented. A discussion of various tools for ontology creation and authoring is presented. This is followed by a discussion of approaches for semi-automatic bootstrapping and generation of ontologies; ontology matching; and ontology management and versioning. Finally, the role of rule-based approaches for representation and reasoning with ontologies will be presented.

6. Ontology Authoring and Management

Ontologies are a critical component of the Semantic Web architecture. In this chapter, we present a discussion on various aspects of ontology authoring and management. We discuss a collection of ontology building tools and present an evaluation across various dimensions. A brief discussion on techniques for boostrapping of ontologies is presented along with a discussion on techniques of integration, merging and versioning of ontologies.

7. Applications of Metadata and Ontologies

A key value proposition enabled by the use of metadata descriptios based on concepts from domain specific ontologies, is the ability to describe Web and other types of content using semantic descriptions with fine grained abstractions. These descriptions could appear in the form of annotations in the case of unstructured data. Alternatively, in the case of structured data created according to a well defined schema, these descriptions can be created based on a mapping between the schema and a domain specific ontology. These metadata descriptions may also be used to query the underlying structured data as well. Finally, with the mappings between the schema and domain ontologies form a critical component, that enables domain ontolog driven information integration. In this chapter, we discuss:

•

Structured and semi-structured metadata annotations of unstructured and semistructured documents on the Web. Tools and techniques to support metadata annotation are presented in Section 7.1.

•

Structured metadata annotations of structured Web resources with a welldefined set of types and schemas. Techniques to support schema and ontology mapping are discussed in Section 7.2.

•

Approaches for ontology driven information integration are discussed in Section 7.3.

Process Aspects of the Semantic Web

Frontmatter

8. Communication

The Semantic Web would be impossible without the advent of simple and efficient communication networks that allow any user connected to the Web to access any public Semantic Web site without effort, very efficiently and extremely fast (most of the time). The basis for this ease of access is a very simple data format for specifying Semantic Web pages and a very simple communication protocol for their access. Both can be easily implemented on any computing platform. This ease of implementation ensures that everybody can participate independent of their particular computing equipment.

9. State of the Art in Web Services

This Chapter introduces the current state-of-the-art in Web Services in the form of various standard proposals that are being worked on currently or that are already implemented in software products. It starts with a brief introduction into the history of Web Services in Section 9.1 and continues with the description of traditional Web Services in Section 9.2. Section 9.3 provides an overview of the standards activities that are ongoing in the area as well as already achieved standards. Web Service composition, as a specifically important area, is called out separately in Chapter 10.

10. Web Service Composition

Web Services are often invoked in isolation, meaning, a Web Service operation provided by a Web Service provider is invoked by a Web Service requester. Based on the input message, the operation provides the result in form of an output message. However, in many cases an individual invocation is insufficient to achieve a more complicated communication or execution scenario that a Web Service requester needs to achieve, especially in the case of long-running communication as discussed in Section 8.3. In this case, several Web Service operations have to be invoked in a specified order to achieve the final outcome. For example, when an invoice for a patient is to be put together, several services are invoked to retrieve the patient’s address, to obtain the line items that require payment, to compute the total amount the patient is liable for, and so on. The end state of the invoice is therefore the result of a series of service invocations. Web Service composition is the concept that provides a means for defining and executing explicitly long-running communication involving several Web Service invocations in an explicitly specified way.

11. Semantic Web Services

Semantic Web Services focus on extending traditional Web Services such that their meaning is embedded in the syntactical description. A lot of work, especially in academia, is devoted to this space and the current status and achievements will be highlighted in this chapter. In Section 11.1 the reasons for Semantic Web Services and the main extensions to traditional Web Services are introduced. While some efforts are based on the development of Semantic Web languages, other efforts that are introduced in Section 11.2 use alternative approaches. Section 11.3 discusses in detail the current Semantic Web Service approaches that are based on the technologies developed in the Semantic Web community. Two very “hot topics” in the space are discovery and composition, both of which are discussed in Section 11.4. Section 11.6 provides a summary.

Standards

Frontmatter

12. Semantic Web Standards

As in many areas it is important to work on standardization to allow widespread development of interoperable software. In the end, this is what counts as success. Consequently, the Semantic Web communities engaged in this process through various means are presented in this chapter.

Putting it All Together and Perspective

Frontmatter

13. A Solution Approach to the Clinical Use Case

We now revisit functional requirements presented in Chapter 2 and illustrate them with examples based on the use case. We begin with a simplified clinical workflow in Figure 13.1 (which is an adaptation of Figure 2.1). This process is used as a (simplified) entry point into the translational medicine use case discussed earlier.

14. Outlook: The Good, the Bad and the Ugly?

In the introduction of this book we wrote: “The Semantic Web is a vision: the idea of having data on the Web defined and linked in a way that it can be used by machines not just for display purposes, but for automation, integration and reuse of data across various applications. The goal of the Semantic Web initiative is as broad as that of the Web: to create a universal medium for the exchange of data. It is envisaged to smoothly interconnect personal information management, enterprise application integration, and the global sharing of commercial, scientific and cultural data.”

Backmatter

Titel: The Semantic Web
verfasst von: Vipul Kashyap
Christoph Bussler
Matthew Moran
Verlag: Springer Berlin Heidelberg
Electronic ISBN: 978-3-540-76452-6
Print ISBN: 978-3-540-76451-9
DOI: https://doi.org/10.1007/978-3-540-76452-6