  Service composition aims at achieving a business goal by composing existing
service-based applications or components. The response time of a service is
crucial especially in time critical business environments, which is often
stated as a clause in service level agreements between service providers and
service users. To meet the guaranteed response time requirement of a composite
service, it is important to select a feasible set of component services such
that their response time will collectively satisfy the response time
requirement of the composite service. In this work, we use the BPEL modeling
language, that aims at specifying Web services. We extend it with timing
parameters, and equip it with a formal semantics. Then, we propose a fully
automated approach to synthesize the response time requirement of component
services modeled using BPEL, in the form of a constraint on the local response
times. The synthesized requirement will guarantee the satisfaction of the
global response time requirement, statically or dynamically. We implemented our
work into a tool, Selamat, and performed several experiments to evaluate the
validity of our approach.
