SysML FAQ: What is a State Machine diagram (SMD) and how is it used?
What is a SysML State Machine diagram?
Definitions
State: A State (notation: rounded-rectangle a.k.a. "roundangle") represents a condition or situation during the life of an object during which it satisfies some condition, performs some activity, or waits for some event.
State Machine diagram (smd): An State Machine diagram is a dynamic behavioral diagram that shows the sequences of States that an object or an interaction go through during its lifetime in response to Events (a.k.a. "Triggers"), which may result in side-effects (Actions.
Purpose
The purpose of State Machine diagrams is to specify dynamic system behaviors for time-critical, mission-critical, safety-critical, or financially-critical objects. When properly applied (See Usage Notes below) State Machine diagrams are recursively scalable and simulatable.
Top-Level State Machine
Diagram Properties
| Diagram Name | Diagram Type | UML 2 Analog | SDLC Usage | Essential AGILE SYSML? |
Dynamic Sim † |
Math Sim ‡ |
Auto Code Gen |
Rigor | Semi | Informal |
|---|---|---|---|---|---|---|---|---|---|---|
| State Machine diagram (stm) | Dynamic Behavior [Simulatable] |
State Machine | System Analysis, System Design |
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Usage Notes
| BEST PRACTICE PATTERNS |
ANTI-PATTERNS |
|---|---|
| * Use Activity and Sequence diagrams to specify collaborative dynamic behaviors; use State Machines selectively for time/safety/mission/financial critical objects. | * SMactivity Anti-Pattern = Conflate State Machine and Activity syntax and semantics. |
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