Dynamic Web Services Composition - An Aspect Oriented Approach

Abstract

Service Oriented Architecture (SOA) has gained considerable interest in recent years, mostly due to the advent of standards-based Web services that simplify interoperability, loose-coupling and realization of SOA, one of the basic business motivations for implementing SOA today is achieving business agility, as SOA can help businesses respond more quickly and cost-effectively to changing market-conditions. It can also simplify interconnection to existing IT (legacy) assets as well as reconfiguring loosely coupled business services in a simple, fast and low cost manner. For SOA to succeed in that, it is a key issue to provide a dynamic Web service composition approach to facilitate business innovation and adapt IT to today's fast changing markets. Currently the industry standard web services composition language is BPEL (Business Process Execution Language) which has gained a large support from the industry since its start, however the lack of support for dynamic composition of services during runtime in BPEL is a major issue that motivated many researchers to overcome this deficiency, one of the successful solutions that approached this problem is AO4BPEL(Aspect Oriented for BPEL) which proposed using Aspect Oriented Programming techniques (AOP) to achieve dynamism in BPEL. In this paper, we propose an extension to BPEL (Business Process Execution Language) to achieve dynamic web services composition based on a dynamic approach for AO4BPEL. First, a dynamic approach for AO4BPEL is introduced, in that approach we propose an extension to AO4BPEL in order to allow it to dynamically generate aspects during runtime. then a BPEL container that makes use of AOP by implementing Dynamic AO4BPEL engine is created. Following that an enhancement is introduced to the BPEL language by the introduction of <extendedInvoke> tag which replaces the normal <invoke> tag in BPEL. The engine makes use of the <extendedInvoke> tag to determine which web service to be chosen during runtime. Finally, by performing BAM (Business Activity Monitoring) on the business process and web services, the qualified web services can be dynamically selected and bound into the business process. A prototype system has been developed and is also delivered to demonstrate the effectiveness of that approach.