IJCSNS International Journal of Computer Science and Network Security, VOL.7 No.9, September 2007 90 Manuscript received September 5, 2007 Manuscript revised September 20, 2007 Quality Information Modeling for QDD Support Laila Fetjah, Abderrahim Sekkaki Department of Mathematics and Computer Science University Hassan II, Ain Chock, Faculty of Sciences P.O Box 5366, Mâarif – Casablanca, Morocco. Summary Nowadays QoS (Quality of Service) architectures have been required to support most of distributed applications, particularly in wide environments like the Internet. In this context, it aims to be more interesting to offer services according to user requirements and expectations. We will be able to talk about Quality Driven Delivery (QDD) when we consider the users expectations in terms of non-functional requirements like cost. In this paper, we propose a framework to support QDD in distributed multimedia systems that enable QoS specification, QoS mapping and more generally QoS decisions in order to provide resources allocation and adaptation. We focus on the quality information management to support QDD while proposing an UML diagram for QoS information model. Key words: QDD, QoS and Distributed Multimedia System 1. Introduction During these last years, the world of business was revolutionized by the appearance of new applications such as electronic commerce, News-On-Demand or Video-On- Demand. These applications allow the companies to reach more customers by offering them an outfit of services, and so increase their productivity and their flexibility. These applications use generally distributed multimedia systems, which have the peculiarity to integrate several media such as sound, images and video sequences. Thus, it would be necessary to supply to these applications some system management mechanisms that must offer QoS support, application adaptation and system scalability [3]. For example, a VoD application needs a certain bandwidth so that the passed on images are correct. System scalability presents the system capacity to evolve according to the met loads. Application adaptation concerns the capacity of the system to change its behaviour according to the variations in the processing environment. QoS management is a general concept, which represents all the techniques allowing to guarantee that a distributed system offers the QoS level required by users or applications. Generally, a user specifies his or her requirements, which concern system performance, and the system has to deliver the specified level by transforming the user specifications, in constraints aiming at the transport layer [12]. Most of QoS-related research works are interested in resources allocation, few of them are interested in content adaptation or the quality perceived by the user. New approaches have to consider the user in the first rank by taking into account user-perceived QoS characteristics which must be then transformed into constraints targeted the actors of the distributed multimedia system. We are talking about Quality-Driven-Delivery (QDD)[8], where the objective is to supply services by considering the quality level specified by the user. The QDD allows offering and support levels of service adapted to users requirements by offering them the specification of non- functional requirements. The QDD resumes some QoS activities like specification, monitoring and mapping [8]. Quality information is going to act in these activities and is generally going to come from different sources what make them heterogeneous in their definition, representation and manipulation. Therefore, the need of homogenization of this information is indispensable. More particularly, an approach based on modeling and model management is imperative for the extension and the adaptation of quality information models. This modelling is going to allow separating QoS management from QoS information management in order to make them independent from the systems that implement them. In the majority of existing architectures (i.e. QoSME, QuO, TAO and OMEGA) [5] [6] [13] [14] [17] [20], information models are defined by an ad-hoc way and remain very dependent on their architectures what makes their interoperability quasi impossible. In this paper, we will focus on quality information management to support QDD. More particularly we shall propose architecture for QDD management in a distributed context and we shall present an UML model for QDD information management. The rest of the paper will be organized as follows: Section 2 explains the difference between QoS and QDD by emphasizing on the necessity of directing towards this new notion. Section 3 gives a brief review of some