The System Modes Model is a dynamic view of the various states of a system and the transitions between them. These states or modes significantly affect the system's responses to the outside world. You use a State Diagram to document the System Modes Model, where a Subsystem is the parent of the State Diagram (through a State Machine).

Unlike the Dynamic Model, which also uses the State Diagram, the System Modes Model describes states that affect the entire system. In contrast the Dynamic Model shows more localized states for an object.

System Modes may affect the validity of certain Use Cases. For example, it may be feasible to apply a Run Maintenance Checks use case when a system is in the Maintenance mode, but not while that system is in the Normal Operation mode.

The State Diagram shows allowable modes and the events that cause the transition between modes. In general, a State Diagram used for System Modes Modeling requires less detail than State Diagrams used for Dynamic Modeling.

The State Diagram can also show Event Action Blocks. For the System Modes Model you need not describe your diagram to this detail.

You can model the System Modes Model through a General Flow Diagram. For more information about General Flow Diagrams, see Overview of general flow diagrams.