the runtime environment in which a virtual machine operates. It is defined by three sets of names: input names represent the control properties of all available variables output names represent the available actions on the variables state names, as defined for each of the states of the FSM. The input names build virtual conditions to perform state transitions or input actions. The virtual conditions are built using the positive logic algebra. The output names trigger actions; entry actions, exit actions, input actions or transition actions. Positive Logic Algebra The rules to build a virtual condition are as follows: Input Names and Virtual Input A state of an input is described by Input Names which create a Set: input A: Anames = {A1, A2, A3} input B: Bnames = {B1, B2} input C: Cnames = {C1, C2, C3, C4, C5} etc. Virtual Input VI is a set of mutually exclusive elements of input names. A VI always contains the element always: VI = {always} VI = {always, A1} VI = {always, A1, B2, C4} Logical operations on Input Names & (AND) operation is a set of input names: A1 & B3 & C2 => {A1, B3, C2} | (OR) operation is a table of sets of input names: A1 | B3 | C2 => ~ (Complement) is a complement of a set of input names: ~A2 = {A1, A3} Logical expression A logical expression is an OR-table of AND-sets (a disjunctive normal form): A1 & B3 | A1 & B2 & C4 | C2 => Logical expressions are used to express any logical function. Evaluation of a logical expression The logical value (true, false) of a logical expression is calculated by testing whether any of the AND-sets in the OR-table is a subset of VI. Output Names and Virtual Output A state of an output is described by Output Names which create a set: output X: Xnames = {X1, X2} output Y: Ynames = {Y1, Y2, Y3} Virtual output VO is a set of mutually exclusive elements of output names. Virtual Environment The Virtual Name and Virtual Output completed by State Names create the Virtual Environment VE where the behaviour is specified. VFSM Execution Model A subset of all defined input names, which can exist only in a certain situation, is called virtual input or VI. For instance temperature can be either "too low", "good" or "too high". Although there are