A Model of Evolvable Components

We present a model of components following the process calculus approach. The main problem was isolating primitives that capture the relevant concepts of component-based systems. The key features of the calculus are: a hierarchical structure of components; a prominent role to input/output interfaces; the possibility of stopping and capturing components; a mechanism of channel interactions, orthogonal to the activity of components, which may produce tunneling effects that bypass the component hierarchy. We present the calculus, explain the syntax, formulate its operational semantics and a basic type system. We show a number of examples of use of the calculus, with particular emphasis to common evolvability patterns for component