FlexTV is a reference middleware platform developed in the context of the Brazilian Digital TV project. The first FlexTV version did not use a component model which could make it possible to reconfigure the middleware at runtime. This paper presents a component model which was designed to be used in embedded systems, like Set-Top Boxes and Digital TV sets. The proposed model was used to implement a new version of the FlexTV middleware and to incorporate some functionality to that middleware which made it possible to reconfigure its components at runtime. Therefore, this work also presents a high level architecture for a mechanism that can be used to generate a representation of the middleware's execution context. Such a representation can be used to identify the components which need to be reconfigured, aiming to make the middleware more suited to its execution context. RESUMOO FlexTV é uma proposta de middleware de referência desenvolvida para o Sistema Brasileiro de TV Digital. Apesar de ter uma arquitetura modular, a primeira versão do FlexTV não utilizou um modelo de componentes que possibilitasse a sua reconfiguração em tempo de execução. Este trabalho apresenta um modelo de componentes projetado para ser utilizado em sistemas embarcados como, por exemplo, Set-Top Boxes(STB) e aparelhos de televisão digital. O modelo proposto foi utilizado no middleware FlexTV agregando a este funcionalidades que tornaram possível a reconfiguração (adição, remoção e substituição) dos seus componentes em tempo de execução. Além disso, esse trabalho apresenta a arquitetura de alto nível de um mecanismo que possibilita que seja gerada uma representação do contexto de execução de middlewares. Tal representação pode ser utilizada para identificar quais componentes precisam ser reconfigurados, visando tornar o middleware mais adequado ao seu contexto de execução corrente.

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Nowadays, one of the most challenging tasks in component-based software development processes is to discover suitable reusable assets that fulfill the requirements of a particular software system under development. In such a context, this paper presents an XML-based asset representation model for describing all kinds of software assets that can be produced or reused within componentbased software development processes. The proposed model is based on asset metadata that provides effective means for developing universal repository systems that can deal with discovery, retrieval and composition of software components.

Context-aware systems are able to monitor and automatically adapt their operation accordingly to the execution context in which they are introduced. Component-based software engineering (CBSE) focuses on the development and reuse of self-contained software assets in order to achieve better productivity and quality. In order to store and retrieve components, CBSE employs component repository systems to provide components to the system developers. This paper presents an active component repository that is able to receive the current configuration from the context-aware system and compute the components and the new architecture that better fit the given context. Since the repository has a wide knowledge of available components, it can better decide which configuration is more suitable to the running system. The repository applies Fuzzy logic algorithm to evaluate the adequacy level of the components and GRASP algorithm to mount the new system architecture. In order to verify the feasibility of our approach, we use a digital TV middleware case study to achieve experimental results.