 (consists of one state, undressed) and dressed (consists of six states). The set of the states undressed and dressed are then regarded as values of the variable dressState, which is a state class. One bene- fit of this method is that generic transitions can be defined, as indicated in the dia- gram to the right in Fig. 7.46. This diagram reflects a change in the wife's behaviour, implying that she can choose any initial combination of jackets and ties from the undressed state. Without the introduction of the state class dressState, we would need to add another five transitions to the diagram. We can then draw a state diagram where the state class dressState is taken as the explicit state variable, see Fig. 7.47. The difference from EFSM diagrams based on explicit states is that the definition of pre- and postconditions become more com- plex, since conditions must be based on more variables. Note also that if too much of the behaviour information is covered by pre- and postcondition statements, the diagram loses its meaning. The best approach to transforming complex FSM dia- grams to EFSM diagrams is to combine explicit states and state classes. {dressState undressed} pre: {jacket grey} & {tie yellow} pre: {jacket white} & {tie blue} post: {jacket white} post: {jacket red} pre: {jacket grey} & {tie yellow} pre: {jacket grey} & {tie blue} post: {jacket red} post: {jacket grey} {dressState dressed} pre: {jacket grey} & {tie yellow} pre: {jacket grey} & {tie blue} post: {jacket white} & {tie blue} post: {jacket white} & {tie yellow} pre: {jacket red} & {tie yellow} pre: {jacket white} & {tie yellow} post: {jacket red} & {tie blue} post: {jacket grey} & {tie yellow} Fig. 7.47 EFSM representation of the same FSM diagram based on the state class dressState Active state, reactive state, interrupt state, pending state: A port, at a particular point in time, is either in an active state or in a reactive state. The distinction is: 7.5 Behaviour Descriptions An active state is a transient state. When in an active state, the