Complex systems’ specifications and design documents define their states and modes using plain language instead of formal specification methods. So it is necessary to have a practical approach for defining requirements to be incorporated into the functional definition of such systems.
Definitions
- State: the overall condition of a system or a subsystem. May be related hierarchically. Are exclusive.
- Status: an indication from a system or subsystem as to its own determination of its state, mode and/or condition(s).
- Mode: the way in which functions are performed. Exist within states. May be exclusive or concurrent. Function execution related to modes.
- Condition: an attribute of the system at a particular point in time. May contribute to the derivation of a system’s state, mode or transitions.
- Function: a capability, activity or basic operation of the system.
Model diagram
A system may be defined to exist in zero or more states. States may consist of zero or more substates. A mode may execute in one or more states. A function may be performed in one or more modes. The system must perform one or more functions. Functions may be decomposed further (not shown).
References
This post was originally written on a previous blog experiment on 2014/04/04 13:34