Extension of the Fractal ADL for the Specification of Behaviours of Distributed Components

Inheriting from a long experience about modules, objects and interfaces, component programming has emerged as a programming methodology ensuring both re-usability and composability. Among the components models, Fractal [6] provides hierarchical composition for a better structure, and specification of control interfaces for dynamic management. Fractal defines a highly extensible component model which enforces separation of concerns, and separation between interfaces and implementation. The Fractal Architecture Definition Language (ADL) is an extensible language allowing one to define a component architecture to be defined by statically specifying the structure and content of a component system. A component can be instantiated by passing its ADL definition to a factory. Synchronous and Asynchronous implementations: the Fractal model does not specify how communications are done. There are implementations with synchronous (e.g. Julia [3]) and with asynchronous method invocation (e.g., ProActive [10]), so behaviour specification and verification must respect this heterogeneity. The Dream [2] framework mixes synchronous and asynchronous communications through composite bindings, and in the context of potentially distributed components some implementations directly mixing synchronous and asynchronous communications (depending on the interfaces involved) should come out. The Grid Component Model is a component model focusing on Grid applications, that is currently being designed inside the CoreGrid Network of Excellence. It is proposed as an extension of the Fractal component model, integrating the specificities of Grid computing that need to be taken into account in the definition of the GCM. Fractal was chosen as the reference model for designing the GCM because it is a simple though extensible model with clear specifications. At some point, the GCM standard will probably lead to a proposal for an extension of the Fractal ADL. Multicast and Gathercast Interfaces: to meet the specific requirements and conditions of multiway communications (1-to-n, n-to-1 or n-to-n), for distributed components systems in general, and for Grid computing in particular, multicast and gathercast interfaces give the possibility to manage a group of interfaces as a single entity, and expose the collective nature of a given interface.