A virtual finite-state machine (VFSM) is a finite-state machine (FSM) defined in a Virtual Environment. The VFSM concept provides a software specification method to describe the behaviour of a control system using assigned names of input control properties and output actions. The VFSM method introduces an execution model and facilitates the idea of an executable specification. This technology is mainly used in complex machine control, instrumentation, and telecommunication applications. Why Implementing a state machine necessitates the generation of logical conditions (state transition conditions and action conditions). In the hardware environment, where state machines found their original use, this is trivial: all signals are Boolean. In contrast state machines specified and implemented in software require logical conditions that are per se multivalued: Temperature could be Low, OK, High Commands may have several values: Init, Start, Stop, Break, Continue In a hierarchical control system the subordinate state machines can have many states that are used as conditions of the superior state machine In addition input signals can be unknown due to errors or malfunctions, meaning even digital input signals (considered as classical Boolean values) are in fact 3 values: Low, High, Unknown. A Positive Logical Algebra solves this problem via virtualization, by creating a Virtual Environment which allows specification of state machines for software using multivalued variables. Control Properties A state variable in the VFSM environment may have one or more values which are relevant for the Control—in such a case it is an input variable. Those values are the control properties of this variable. Control properties are not necessarily specific data values but are rather certain states of the variable. For instance, a digital variable could provide three control properties: TRUE, FALSE and UNKNOWN according to its possible boolean values. A numerical (analog) input variable has control properties such as: LOW, HIGH, OK, BAD, UNKNOWN according to its range of desired values. A timer can have its OVER state (time-out occurred) as its most significant control value; other values could be STOPPED or RUNNING. Actions Other state variables in the VFSM environment may be activated by actions—in such a case it is an output variable. For instance, a digital output has two actions: True and False. A numerical (analog) output variable has an action: Set. A timer which is both: an input and output variable can be triggered by actions like: Start, Stop or Reset. Virtual Environment The virtual environment characterises