A scheme for quality of service management in distributed applications

Builders of object-oriented distributed applications have to cope with many complex problems. One of these problems is the control of object interactions when the interacting entities are on different sites on a network. Such interactions are subject to performance drops or network failures. Managing the application behavior in these situations is difficult to achieve: a simple timeout scheme is often not powerful enough to keep the whole application’s state consistent and under control. In this paper we present a scheme which provides various means for defining and configuring distributed objects interactions. The scheme is based on an inter-object contract concept. It allows the distributed software designer to manage, tune and extend contracts. A set of predefined contracts allows the specification of time-based constraints. The contract scheme has been implemented as a distributed framework which provides soft real-time services for a computer supported cooperative work platform. Key-words: distributed application, CSCW, distributed framework, contract, quality of service, Java