Quality-of-service specification in distributed object systems

Abstract

Traditional object-oriented design methods deal with the functional aspects of systems, but they do not address quality-of-service (QoS) aspects, such as reliability, availability, performance, security and timing. However, deciding which QoS properties should be provided by individual system components is an important part of the design process. Different decisions are likely to result in different component implementations and system structures. Thus, decisions about component-level QoS should commonly be made at design time, before the implementation is begun. Since these decisions are an important part of the design process, they should be captured as part of the design. We propose a general quality-of-service specification language, which we call QML. In this paper we show how QML can be used to capture QoS properties as part of designs. In addition, we extend UML, the de facto standard object-oriented modelling language, to support the concepts of QML.