A Community-based Approach for Application Composition in a Peer-to-Peer Environment Elie Abi-Lahoud, Marco Viviani, Kokou Yetongnon Universit´ e de Bourgogne – Sciences et Techniques Laboratoire LE2I – Mirande, Aile de l’Ingenieur 9 av. Savary – 21078 Dijon Cedex France Email: {elie.abi-lahoud, marco.viviani, kokou.yetongnon}@u-bourgogne.fr Abstract The design of composite applications by combining ex- isting services with known semantics is an ongoing topic in current research. Several studies are aimed at provid- ing service description models and standards, service dis- covery and matching etc. However, service composition in distributed dynamic environments such as P2P has received little attention from the research communities. In this pa- per we present a design framework for composing services, taking in particular into account different ways for building peer-communities based on network or services character- istics. 1 Introduction The increasing interest in service oriented applications and systems is spurred by the development of dynamic and pervasive computing networks such as P2P systems that support resource sharing among computers or communities of users. The goal is to design composite applications by combining existing service components with known seman- tics. The importance of service oriented systems stems from two main facts: (i) the progressive shift in software design from traditional approaches where applications are speci- fied and designed from scratch or are re-engineered from existing applications to meet new requirements, and (ii) the increasing need for flexible and adaptable design capable of quick reaction to changes in both user requirements and computing infrastructure. On-demand service-based appli- cation design requires a precise description of services if semi-automatic composition based on agreed upon seman- tic is used. Previous work in service oriented systems has focused to a significant extent on what services are, linguis- tic constructs and models to define and represent service behaviors and properties, architectures or protocol suites to allow service sharing, and how services can be functionally matched, composed or orchestrated into more complex sys- tems [2, 3, 5, 8]. 1.1 Objectives and Contributions In this paper we address the service composition is- sue in a peer-to-peer environment. We build on top of an unstructured system a hybrid overlay network, where peers are organized into communities based on selected net- work/services properties. In such an environment, our ap- proach consists of first defining an application as a graph of abstract services, then realizing the application by instanti- ating the graph. We show how service composition can take advantage of the network reorganization in peer communi- ties, in terms of communities definition and communication protocol. The remainder of the paper is organized as follows. Af- ter having detailed in Section 2 the properties used to build communities, we present in Section 3 a multi-level graph- based framework for the composition of services. Section 4 illustrates a concrete scenario and provides two examples of community-based overlay networks. Finally Section 5 concludes the paper and presents future work. 2 Communities in a Service-based Environ- ment From a design point of view, services are building blocks that can be composed into more complex services or ap- plications. Typically, a community of users can share col- lections of services if their functional behaviors are well known and agreed upon and their interfaces in terms of abstract concepts and related parameters are precisely de- scribed. The community of peers can be based on (i) net- work characteristics and (ii) properties connected to ser- vices: 2008 IEEE International Conference on Signal Image Technology and Internet Based Systems 978-0-7695-3493-0/08 $25.00 © 2008 IEEE DOI 105 2008 IEEE International Conference on Signal Image Technology and Internet Based Systems 978-0-7695-3493-0/08 $25.00 © 2008 IEEE DOI 105 2008 IEEE International Conference on Signal Image Technology and Internet Based Systems 978-0-7695-3493-0/08 $25.00 © 2008 IEEE DOI 10.1109/SITIS.2008.102 105 2008 IEEE International Conference on Signal Image Technology and Internet Based Systems 978-0-7695-3493-0/08 $25.00 © 2008 IEEE DOI 10.1109/SITIS.2008.102 105