1 Introduction
Service-oriented computing has become an important paradigm for deploying software. A “service” may be defined as a behaviour that is provided by a software component, for use by another, based only on an interface. The interface acts as a contract between services, enabling the discovery, advertising, delegation and composition of services [1]. Most contracts at present are addressing the functional interface of a service - generally describing aspects such as called and return parameter types, and exception handlers. In our framework we emphasise non-functional attributes of a service - primarily its QoS. We define QoS at three different levels: at the application level, at the middle-ware level, and at the network level - and suggest how these three different aspects can be combined to support service management. This work is based on our G-QoSM frame-work, described in detail in [3].