A Typing Scheme for Behavioural Models

State machines can be used to specify the behaviour of objects in a system by describing the relationships between the states of the object and its ability to respond to events presented to it. Suitable choice of semantics for state machines allow multiple machines to be composed in the description of a single object. We describe an extension to this approach whereby different machines in the composition of a single object have different semantic types covering necessary behaviour, encouraged behaviour and discouraged behaviour. This provides expressive power to model the way software interacts with the domain to encourage or discourage events.