Grid computing has emerged as an important new field, distinguished from conventional distributed computing by its focus on large-scale resource sharing, innovative applications, and, in some cases, high-performance orientation. QoS-aware service composition is a key requirement in Grid environments since it enables users to fulfill his/her required complex tasks while meeting different global Quality of Service (QoS) constraints. The problem of QoS-aware grid service composition is known to be a NP-hard problem. In this paper a novel Ant Colony Optimization (ACO) algorithm is proposed for QoSaware grid service composition to find near optimal composite service. This paper also presents a...