• Introduction
• Collaboration diagrams
• State diagrams
  • How many state diagrams are needed?
• Activity diagrams

Collaboration and State Modeling

Introduction

• Model additional aspects of your system.
• Most useful in real-time system design.
• Collaboration diagrams are similar to sequence diagrams.

Collaboration diagrams

• Shows how critical objects collaborate within a use case.
• Collaboration diagrams are similar to sequence diagrams.
  • Collaboration diagrams focus on key transactions.
  • Sequence diagrams follow the flow of entire use cases (emphasis on time ordering).
  • Collaboration diagrams add extra detail related to timing of messages.

State diagrams

• Captures the lifecycle of one or more objects.
• Expressed in terms of:
  • Different states objects can assume
  • Events that cause changes in state

Basic elements:

• Initial state - hollow circle containing a black dot.
• Each additional state - rectangle with rounded corners.
• Three standard events:
  • Entry
  • Exit
  • Do
• Transition - an arrow between two states.

How many state diagrams are needed?

• Every object has a state machine.
  • Object is created.
  • Sends messages.
  • Receives messages.
  • It is destroyed.
• In reality, most state machines are boring, so don't waste time drawing them.
  • Don't diagram an object with two states, On and Off.
• Readability is important.

Activity diagrams

• Remarkably similar to flowcharts.
• Swimlanes - group a set of activities according to who is performing them.
• A good way to understand/model business processes.