XCompose: A Framework for Flexible, Extensible, Reusable and Correct Component Composition

With increasing number of components now available on the market, research and industry empha-sis has shifted from the development of component models to the development of languages and other techniques to enable the composition of pre-fabricated components. We believe that frameworks for composition of components must be flexible, extensible, re-usable and must at the same time provide guarantees on the correctness of the composition. In this paper, we present an XML-based component composition framework, namely XCompose, that is based on (1) the simple hypothesis that complex component compositions can always be broken down into a sequence of primitive composition opera-tors; and (2) the paradigm “applications = components + composition language ” where “composition language = operators + glue logic”. Based on this hypothesis and paradigm, we define a set of operators and show how operators can be effectively combined to formulate arbitrary component compositions via composition pattern, thereby enabling flexibility and extensibility. In this paper, we take a step further and introduce the notion of composition templates that facilitate the re-usability of component compositions. To address the problem of composition correctness, we introduce contracts as a mechanism to specify pre- and post-conditions for both individual compositions as well as for entire applications. Lastly, we present an architectural overview of XCompose, our XML-based composition framework