THE emerging area of Service-Oriented Computing
(SOC) has drawn a great deal of attention
in recent years, prompting researchers to devise a
variety of technologies to facilitate loosely coupled
and flexible SOC architectures. Web services are autonomous
application modules that can be described,
published and located in SOC environments. To build
a complex application, one may have to link a set of
service providers across their heterogeneous environments
. Service composition fulfills users’ requirements
by combining services in different repositories.
The users’ requirements can be functional or nonfunctional.
The functional requirements are in relation
to the overall outcome concerning the functionalities
of the business process, while the non-functional requirements
pertain to the quality of the composition
as a whole, e.g., availability, reliability, cost and response
time. As the number of web services, providing
similar functionalities, grows large, the problem
of selecting web services with the best guaranteed
Quality of Service (QoS) becomes critical.