Emerging Web services standards enable the development of large-scale applications in open environments. In particular, they enable services to be dynamically bound. However, current techniques fail to address the critical problem of selecting the right service instances. Service selection should be determined based on user preferences and business policies, and consider the trustworthiness of service instances.We propose a multiagent approach that naturally provides a solution to the selection problem. This approach is based on an architecture and programming model in which agents represent applications and services. The agents support considerations of semantics and quality of service (QoS). They interact and share information, in essence creating an ecosystem of collaborative service providers and consumers. Consequently, our approach enables applications to be dynamically configured at runtime in a manner that continually adapts to the preferences of the participants. Our agents are designed using decision theory and use ontologies. We evaluate our approach through simulation experiments.
Current Web services standards enable publishing service descriptions and finding services on a match based on criteria such as method signatures or service category. However, current approaches provide no basis for selecting a good service or for comparing ratings of services. We describe a conceptual model for reputation using which reputation information can be organized and shared and service selection can be facilitated and automated.
MOTIVATIONWeb services promise the dynamic creation of loosely coupled information systems. However, current approaches are logically centralized and lack key functionality, especially to locate, select, and bind services meeting certain criteria of quality. Recently, we developed an architecture that uses software agents who serve as proxies for clients and interact with one or more agencies through which service reputations and endorsements are disseminated. However, this and other service architectures leave open some key semantic questions. Specifically, a proxy should be able to discover and understand new service attributes from their descriptions, especially as they evolve over time, and an agency should be able to aggregate the right information about service quality and present it suitably formally described that they can be understood by proxies.We address these semantic questions by developing a conceptual model of a service provider's reputation for delivering quality services. The conceptual model has a generic component (e.g., attribute types and common attributes such as price, on-time delivery, and so on) and can be enhanced with domain-specific components (e.g., closeness of itinerary to desired times, which makes most sense for services in the travel domain). By combining ser-"We are indebted to Amit Chopra, Ashok Mallya, Amit Sheth, Raghu Sreenath, and Pmar Yolum for useful comments. This work was supported by IBM and the National Science Foundation under grant ITR-0081742.vice considerations with semantic web representations, this work fits into the recent activity on semantic Web services.
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