Service Selection with Runtime Aspects:A Hierarchical Approach

The composition of services is used to implement complex functionality. The quality of service (QoS) is a demanding issue for the management of service compositions. A QoS-aware service selection recommends the services to be composed to account for the quality of a service composition and its execution cost incurred by requests. It is shown that in the presence of sophisticated service charging a cost minimization objective imposes the need for a request- and service composition-comprehensive service selection.This type of selection is called a tactical service selection. Existing tactical service selection models assume a deterministic executionenvironment. The need to adjust a service composition during the execution of a request to react on uncertain QoS attributes and service failures is neglected. Service reconfiguration approaches are proposed to deal with service failures, uncertain QoS attributes, and their impact on QoS restrictions. The challenge addressed in this paper is to propose a hierarchical service selection that integrates a tactical service selection with a service reconfiguration to satisfy the cost minimization objective and to maintain a successful execution of requests. It is shown that the tactical service selection can be efficiently combined with an existing service reconfiguration method to achieve both runtime-related goals and tactical objectives.