  Classical approaches like process algebras or labelled transition systems
deal with static composition to model non-trivial concurrent or distributed
systems; this is not sufficient for systems with dynamic architecture and with
variable number of components. We introduce a method to guide the modelling and
the dynamic composition of processes to build large distributed systems with
dynamic adhoc architecture. The modelling and the composition are based on an
event-based approach that favour the decoupling of the system components. The
composition uses the sharing of abstract communication channels. The method is
appropriate to deal with evolving processes (with mobility, mutation). The
event-B method is used for practical support. A fauna and its evolution are
considered as a working system; this system presents some specificities, its
behaviour is not foreseeable, it has an adhoc (not statically fixed)
architecture.
