Agent-Based Infrastructure for Dynamic Composition of Grid Services

Agent-Based Infrastructure for Dynamic Composition of Grid Services

Matthew Adigun (University of Zululand, South Africa), Johnson Iyilade (University of Zululand, South Africa) and Klaas Kabini (University of Zululand, South Africa)
DOI: 10.4018/978-1-61520-686-5.ch039
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The service-oriented computing paradigm is based on the assumption that existing services can be put together in order to obtain new composite services. This chapter focuses on how peer-to-peer architectures based on multi-agent systems can be used to build highly dynamic and reconfigurable infrastructure that support dynamic composition of grid services. The chapter starts by providing an overview of key technologies for SOC. It then introduces dynamic service composition and challenges of composing grid services. The authors further motivate for Multi-agent system approach in SOC and why it becomes important in service composition. They then present our research effort, AIDSEC, an agent-based infrastructure for dynamic service composition, describing its architecture, implementation and comparison with some related work in the literature. In addition, the chapter raises some emerging trends in SOC and the particular challenges they pose to service composition. They conclude by suggesting that a solution based on multi-agent system is required for composing services that possess capabilities of autonomy, reliability, flexibility, and robustness.
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The Service Oriented Computing (SOC) paradigm is currently a promising methodology for engineering applications in both scientific and industrial communities (Bhatia, 2005). It promises a world of distributed services that are loosely coupled to flexibly create dynamic business processes and agile applications that may span many organizations and computing platforms.

A major assumption of the SOC approach is that services can be combined together in order to obtain new, composite services. The implication of this is that future enterprise and scientific applications do not have to be developed from the scratch but assembled on the fly from an ecosystem of services available on a network such as the grid (NGG Report, 2006). This is already having revolutionary impact on the way software applications are designed, architected, delivered and consumed.

Building scientific or business applications that utilize distributed services is one of the challenges facing the SOC research community today. Traditional software engineering methodologies are often inadequate in addressing the complexity and dynamic nature of large-scale distributed systems. Classical techniques for composing services are procedural and only define how different services ought to be invoked e.g. in terms of ordering and parallelism among them. They are geared for low-level invocation of services, and not specially geared for enabling composition (Singh & Huhns, 2005). Moreover, a number of existing techniques are too rigid and are controlled by a centralized composition engine. They are, therefore, inadequate for service composition, especially, when services require capabilities of autonomy, flexibility and robustness.

Interestingly, there has been an explosion of interest in peer-to-peer (P2P) methodology as a promising approach for engineering large scale distributed systems (Bhatia, 2005). P2P systems generally, offer the advantages of scalability, reliability, and robustness over traditional server-based systems (Verma, 2004). Multi-agent Systems (MAS) have thus, emerged as a P2P methodology that address the issues of organizing large-scale software systems and could, therefore, complement existing methodologies for SOC. Agents are autonomous, computational entities that can be viewed as perceiving their environment through sensors and acting upon them through effectors (Bradshaw, 1997). Many existing and potential industrial applications of multi-agent systems in engineering large-scale systems are found in many fields such as e-commerce, telecommunications, transportation, sensor network, scheduling, and manufacturing (Weiss, 1999). Multi-agent systems would, therefore, be invaluable in emerging SOC environments especially in developing and analyzing intricate models and theories of interactivity and collaboration among Collaborative Virtual Enterprises (CVEs) and Virtual Organizations (VOs). Moreover, agents provide greater flexibility and robustness in how services are used and created by operating rationally in a variety of environmental circumstances and context that change in a usually unforeseen manner.

We, therefore, present in this chapter an approach that augment current service-based technologies with multi-agent system for dynamic composition of grid services.

The rest of the chapter is organized as follows:

Key Terms in this Chapter

Workflow: A workflow is an activity that addresses some need by carrying specified control and data flows among sub-activities that involve information resources and possibly humans e.g loan processing workflow involves: filling out a form, clerk reviews its completeness, auditor verifies information, and a supervisor invokes an external credit agency.

Multi-Agent System: A software agent is a computational entity that can be viewed as perceiving and acting upon its environment and that is autonomous in that its behaviour at least partially depends on its own experience. A multi-agent system consists of a population of agents.

Web Services: A web service is a software system identified by a Uniform Resource Identifier (URI) whose public interfaces and bindings are defined and described using XML–based messages conveyed by Internet protocols.

Dynamic Service Composition: Service composition is the process of putting services together to achieve some desired functionality. The process can be static or dynamic. In dynamic service composition, the creation of the abstract task model and participating services is done at runtime.

Grid Services: A grid service is an interface associated with a grid resource. It is implemented using OGSI or WSRF frameworks. It is a special adaptation of web services technology for grid environment. However, we consider grid services as the de-facto service implementation technology for emerging applications in both scientific and business domain.

Virtual Organizations (VO): These are dynamic group of individuals, groups or organizations who define the conditions and rules for sharing resources in a grid environment. In OGSA, resources are accessed through their service interface. Therefore, the term “resources” could be loosely abstracted to cover a wide range of concepts including physical resources individuals and their expertise, capabilities and frameworks. The resources provided by members of the VO for sharing form the components of the grid service ecosystem.

Service: A service is a coarse-grained, discoverable software entity that exists as a single instance and interacts with applications and other services through a loosely coupled message-based communication model. Service could be implemented using grid service or web service technologies

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