An MDA Approach to Tame Component Based Software Development

The aim of this paper is to show how the Model Driven Architecture (MDA) can be used in relation with component based software engineering. A software component only exhibits its provided or required interfaces, hence defining basic contracts between components allowing one to properly wire them. These contractually specified interfaces should go well beyond mere syntactic aspects: they should also involve functional, synchronization and Quality of Service (QoS) aspects. In large, mission-critical component based systems, it is also particularly important to be able to explicitly relate the QoS contracts attached to provided interfaces with the QoS contracts obtained from required interfaces. We thus introduce a QoS contract model (called QoSCL for QoS Constraint Language), allowing QoS contracts and their dependencies to be modeled in a UML2.0 modeling environment. Building on Model Driven Engineering techniques, we then show how the very same QoSCL contracts can be exploited for (1) validation of individual components, by automatically weaving contract monitoring code into the components; and (2) validation of a component assembly, including getting end-to-end QoS information inferred from individual component contracts, by automatic translation to a Constraint Logic Programming language. We illustrate our approach with the example of a GPS (Global Positioning System) software component, from its functional and contractual specifications to its implementation in a .Net framework.