Contracts for Defining QoS Levels

Multichannel Information Systems provide a way to invoke the same service through several channels. In this way, even if the functionality provided by the service is independent of the actual channel, the quality varies according to the particular devices used by the service consumer. In this context, this paper presents a frame for the creation and management of contracts formalizing the agreement, in terms of quality of service, between an e-Service provider and an e-Service consumer in a multichannel adaptive information system. In particular, the work relates to some of the existing modelling languages for QoS, such as QML, WSLA and XQoS, and presents some extensions to WSLA able to deal with a multichannel environment. The presented model is validated by a prototype developed to support creation and subscription of contracts. The prototype application allows a provider to publish others regarding e-Services with desired QoS parameters, and a consumer to subscribe a contract with the negotiated QoS levels.