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Über dieses Buch

A general architecture for service delivery and coordination in intelligent agent-based peer-to-peer (IP2P) environments, that has been developed within the CASCOM research project, is presented in this book. The CASCOM architecture provides support for business services for mobile workers and users across mobile and fixed networks. To its users, the CASCOM architecture makes easy and seamless access available to Semantic Web Services anytime, anywhere, and using any device. The system has successfully been validated in trials in healthcare applications, in particular in emergency medical assistance.

The CASCOM architecture addresses the problem of seamlessly combining various novel technologies that establish the basis for self-adaptable and self-healing systems including semantic service discovery, matchmaking, composition planning and semantic service composition, reliable execution of composite services, and semantic failure handling. The book provides an in-depth introduction into these areas, presents how they have been extended in order to best support the needs for agent-based service coordination in IP2P environment, and finally shows how the different agents can be seamlessly combined.




Chapter 1. Introduction

The ever-growing number of services on the Web provides enormous business opportunities. In particular, there is a huge potential for creating added value through service coordination. For this to happen, technology must be developed to be capable of pervasively providing and flexibly coordinating ubiquitous business application services to mobile users and workers in the dynamically changing contexts of open, large-scale and pervasive application domains.
Heikki Helin, Michael Schumacher, Heiko Schuldt

State of the Art


Chapter 2. Intelligent Agent-based Peer-to-Peer Systems (IP2P)

One step toward the realization of the CASCOM vision is the development of an intelligent agent-based peer-to-peer (IP2P) environment. IP2P environments are extensions to conventional P2P architectures with components for mobile and ad hoc computing, wireless communications, and a broad range of pervasive devices. Software agents will be a key technology to address the challenges of CASCOM as they offer an adequate abstraction for dealing with services from pervasive devices in IP2P environments. However, agents in wireless environments need support from the underlying architecture. For example, communication over wireless connection needs to be designed carefully. Further, the underlying agent platform shall be tailored to resource-constrained mobile devices.
Heikki Helin, Ahti Syreeni

Chapter 3. Semantic Web Service Description

The convergence of Semantic Web with service-oriented computing is manifested by Semantic Web service (SWS) technology. It addresses the major challenge of automated, interoperable and meaningful coordination of Web services to be carried out by intelligent software agents. In this chapter, we briefly discuss prominent SWS description frameworks, that are the standard SAWSDL, OWL-S and WSML1. This is complemented by a critique, and selected references to further readings on the subject.
Matthias Klusch

Chapter 4. Semantic Web Service Coordination

Semantic service coordination aims at the coherent and efficient discovery, composition, negotiation, and execution of Semantic Web Services in a given environment and application context. What makes coordination of services in the Semantic Web different from its counterpart in the Web is its far more advanced degree of automation through means of logic-based reasoning on heterogeneous service and data semantics.
Matthine Klusch

Chapter 5. Context-Awareness

Context-aware computing has increasingly gained the attention of the research community because, as it is the case with human interactions, context information provides the background against which it is possible to more accurately interpret communicative acts without the need to explicitly state everything that might be relevant. If, within an agent negotiation for buying some specific service, the service provider says “the price is 20 Euros”, the receiver would not be capable of fully interpreting the meaning of the message without using the context created by the whole conversation. Context information provides the basis for more efficient information processing mechanisms due to the possibility of discarding irrelevant information in early stages of information processing. For instance, if some patient’s personal assistance agent is looking for a service that would sell him or her a specific medicine and deliver it in the patient’s home, this would be achieved through the creation of a compound service consisting of an on-line pharmacy and a medicine transportation service. Using context information about the patient’s location, the service composition process may discard service providers located far away from the client and create the compound service considering only a very small number of all existing services of the relevant categories. Context information also enables better adapted behavior since, being context-aware, it may be more directed towards clients requirements in the circumstances of the interaction.
Bruno Gonçalves, Paulo Costa, Luis Miguel Botelho

Chapter 6. Technology in Healthcare

The term “e-health” was born in 1999 to represent the provision of healthcare services through Internet [11], and was heavily promoted by the industry and commercial sectors in order to take advantage of the power and excitement that other “e-” terms like e-commerce and e-business had recently created in society [8, 6]. Nevertheless, the academic world would soon adopt it, leading to what some authors call “the death of telemedicine” [14].
Gert Brettlecker, Céser Cáceres, Alberto Fernández, Nadine Fröhlich, Ari Kinnunen, Sascha Ossowski, Heiko Schuldt, Matteo Vasirani

The CASCOM Solution


Chapter 7. General Architecture

The CASCOM approach is a combination of agent technology, Semantic Web Service coordination, P2P, and mobile computing for intelligent peer-to-peer (IP2P) mobile service environments. IP2P environments (see Chapter 2) are extensions to conventional P2P architectures with components for mobile and ad hoc computing, wireless communications, and a broad range of pervasive devices. Basic IP2P facilities come as Web Services, while their reliable, task-oriented, resource-bounded, and adaptive co-ordination-on-the-fly characteristics call for agent-based software technology.
Alberto Fernández, Sascha Ossowskí, Matteo Vasirani

Chapter 8. Agent Platform and Communication Architecture

The progress in wireless network technologies and mobile devices changes the way in which people can access digital services. A user may access the same services as she would use her desktop computer, but in the nomadic environment she is able to do so anywhere, at any time and even using a variety of different kinds of devices. Such an environment places new challenges on the architecture implementing the services.
Heikki Helin, Ahti Syreeni

Chapter 9. Distributed Directories of Web Services

This chapter presents WSDir, the federated directory system used in CASCOM. Its main functionality is to let heterogeneous Semantic Web Service descriptions be registered and searched by certain clients. As such, it realizes a lookup function with basic retrieval schemes.
Michael Schumacher, Alexandre de Oliveria e Sousa, Ion Constantinescu, Tim van Pelt, Boi Faltings

Chapter 10. Service Discovery

Semantic service discovery is the process of locating Web Services based on the description of their functional and non-functional semantics. Both service oriented computing and the semantic Web envision intelligent agents to proactively pursue this task on behalf of their clients. Service discovery can be performed in different ways depending on the service description framework, on means of service selection, and on its coordination through assisted mediation or in a peer-to-peer fashion.
Luis Botelho, Alberto Fernández, Benedikt Fries, Matthias Klusch, Lino Pereira, Tiago Santos, Pedro Pais, Matteo Vasirani

Chapter 11. Service Composition

One of the striking advantages of Web Service technology is the fairly simple aggregation of complex services out of a library of other composite or atomic services. The same is expected to hold for the domain of Semantic Web Services such as those specified in WSMO or OWL-S. The composition of complex services at design time is a well-understood principle which is nowadays supported by classical workflow and AI planing based composition tools (cf. Chapter 4).
Bastian Blankenburg, Luis Botelho, Fábio Calhau, Alberto Fernández, Matthias Klusch, Sascha Ossowski

Chapter 12. Semantic Web Service Execution

Service execution comprises all the activities that need to be carried out at runtime to invoke one or several (Web) services in a coordinated manner. These activities include initiation, control and validation of service invocations. Since each service is supposed to create side effects as manifested by the functionality that it implements, both the service user and service provider are interested that certain properties for execution are guaranteed. The two most prominent properties are guaranteed termination and reliability, that is, sustaining a consistent state before and after execution even in the presence of failures. Those aspects become of particular interest when it comes to (i) execution in distributed environments where more than one software entity might be involved, and (ii) execution of composite services, i.e., processes.
Luis M. Botelho, António L. Lopes, Thorsten Möller, Heiko Schuldt

Chapter 13. Context-Awareness System

Computer application basic inputs, such as keyboard strokes or pointing devices, supply only limited information about the surrounding environment. The necessity of context information grows as applications need to adapt to the environment in which they are used. This adaptation increases the application’s performance and makes sure that the results are well adapted to the specific circumstances. The main objective of context-aware computing is the development of applications that, without being limited by usual input devices, acquire and use context information to better adapt to the circumstances in which interactions take place.
Paulo Costa, Bruno Gonçalves, Luis Miguel Botelho

Chapter 14. Security, Privacy and Trust

The literature about trust in multiagent systems collects a huge number of works that analyse almost any facets of this concept from nearly every point of view. Nevertheless, an accepted and stable formal model of trust in agent societies is still missing. In this chapter, we address this remarkable flaw of the current research by reporting the main contributions of the CASCOM project on this topic: (i) a stochastic model of trust that measurably captures trust in two-party interactions, and (ii) a general-purpose framework that the CASCOM platform provides to enable the realization of secure, privacy-aware and trust-aware multiagent systems.
Federico Bergenti

Trials and Results


Chapter 15. Qualitative Analysis

Software development aims at providing support for users in order to better cope with specific problems they face in their professional and/or daily life. Thus, developers have to carefully analyze requirements and needs of prospective users. But this process is very difficult and often characterized by misunderstandings between developers and users. In a trial, users evaluate a software application and give valuable feedback whether or not it meets their expectations and how it can be improved.
Mihael Cankar, Nadine Fröhlich, Heimo Laamanen, Thorsten Möller, Heiko Schuldt

Chapter 16. Quantitative Analysis

The different software agents and technologies that were introduced in earlier chapters of this book were also subject to a quantitative evaluation. The main objective of these tests was to verify that they can be effectively used in real world settings. Consequently, the measurements taken are mainly targeted to assess performance and scalability of CASCOM’s meta services. Qualitative measures on the application level are not covered in this chapter and can be found in Chapter 15.
Danilo Bonardi, Luís Botelho, Matthias Klusch, António L. Lopes, Thorsten Möller, Alexandre de Oliveira e Sousa, Matteo Vasirani
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