Optimizing decisions in web services orchestrations

Abstract

Web services orchestrations conventionally employ exhaustive comparison of runtime quality of service (QoS) metrics for decision making. The ability to incorporate more complex mathematical packages are needed, especially in case of workflows for resource allocation and queuing systems. By modeling such optimization routines as service calls within orchestration specifications, techniques such as linear programming can be conveniently invoked by non-specialist workflow designers. Leveraging on previously developed QoS theory, we propose the use of a high-level flexible query procedure for embedding optimizations in languages such as Orc. The Optima site provides an extension to the sorting and pruning operations currently employed in Orc. Further, the lack of an objective technique for consolidating QoS metrics is a problem in identifying suitable cost functions. We employ the analytical hierarchy process (AHP) to generate a total ordering of QoS metrics across various domains. With constructs for ensuring consistency over subjective judgements, the AHP provides a suitable technique for producing objective cost functions. Using the Dell Supply Chain example, we demonstrate the feasibility of decision making through optimization routines, specially when the control flow is QoS dependent. © 2011 Springer-Verlag.