QoS Contract Formation and Evolution

摘要

This paper is concerned with the issues of QoS contract for-rnmation between service providers and consumers and how either party can evolve independently from each other without violating the agreed contract. We show how a QoS contract can be generated using a sub-typing relation on the quality dimensions and value ranges. For that purpose, we use Allen's Interval Algebra (AIA). We also define both strict and relaxed constraints for different dimensions in order to deed with what constitutes acceptable change to different quality dimensions. In particular, we define assertion compatibility as a sufficient condition for ensuring the compatibility of provider and consumer with respect to an existing contract.