  This paper proposes to use dialgebras to specify the semantics of interactive
systems in a natural way. Dialgebras are a conservative extension of
coalgebras. In this categorical model, from the point of view that we provide,
the notions of observation and interaction are separate features. This is
useful, for example, in the specification of process equivalences, which are
obtained as kernels of the homomorphisms of dialgebras. As an example we
present the asynchronous semantics of the CCS.
