Adaptability and Dependability in Dynamic Environments: the Quasi-Synchronous Approach

The widespread of new communication and computation infrastructures creates the potential, and the desire, to build, in that environment, applications with every increasing requirements in what concerns dependability and real-time. However, the dynamic characteristics and type of synchronism usually present on that type of environment (weak synchronism) makes it difficult to achieve that goal. Obtaining cost-effective systems implies the existence of a high level of flexibility and adaptability. That adaptability needs to be done in a timely and safe way so as to not compromise application goals. The quasi-synchronous approach makes it possible to deal with this situation in an effective way. By restricting synchronism requirements to a small part of the system, we are able to obtain synchronous components that can be used to control and validate the other components operation. Timely detection of timing failures and periodic dissemination of control information, allow to build an environment able to support the development of applications offering the desired adaptability and dependability characteristics.