Embedded Systems Development using SysML - Enterprise Architect

Behavior
act Model System Behavior
Start Behavior Modeling
Model Use Cases
Model Finite State
Behav ior
Allocate Requirements to
Use Cases
Allocate Requirements to
State Machines
Model Interactions for Use
Cases
Complete Behaior Modeling
Figure 4 – Roadmap: Model System Behavior
SysML provides four main constructs to represent different aspects of system behavior; use
cases, activity diagrams, sequence diagrams, and state machines.
Our roadmap shows two parallel branches for modeling system behavior. One branch starts
with use cases 3 , which describe scenarios of how users will interact with the system. Use
cases generally consist of a “sunny-day” part which describes a typical success-path for the
scenario, and multiple “rainy-day” parts which describe unusual conditions, exceptions,
failures, etc. Use cases are typically detailed on Interaction (Sequence) Diagrams.
The other branch on the roadmap involves defining event-driven, finite-state behavior of
some part of a system using state machines. As a simple example, there is finite state
behavior associated with the power charging circuitry on our Audio Player. One of Enterprise
Architect’s unique capabilities is the ability to generate functional (algorithmic) code from
state machines. As you’ll see, these state machines can be realized in software or in
hardware using Hardware Description Languages (HDLs).
Requirements are allocated to both use cases and states. Chapter 4 explores behavior
modeling in detail.
3 See “Use Case Driven Object Modeling with UML: Theory and Practice” by Doug
Rosenberg and Matt Stephens for a lot more information about use cases.