Mobile channels for exogenous coordination of distributed systems : semantics, implementation and composition

In the last years, there has been a growing interest for distributed systems both in computer science and in society. The most popular and biggest distributed system in the world is the Internet. A distributed system is a collection of independent computers that appears to its users as a single coherent system. These computers are connected to each other through a network. On each of these computers there is at least one (software) component that needs to communicate with other components on remote computers to achieve some goal. Components can consist of processes, databases, applications, etc. These components are not only distributed among the several computers of a network but they also run in parallel. Therefore, distributed systems need appropriate theory and infrastructures for the coordination of its concurrently running components. In this thesis we present MoCha, a novel coordination framework. MoCha allows dynamic reconfiguration of connections among the components in a system, a property that is very useful and even crucial in systems where the components themselves are mobile. Furthermore, MoCha provides exogenous coordination. This makes it possible to coordinate components from the 'outside' (exogenous), and thus, change a distributed system's behavior without having to change its components.