Use Cases

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Use Cases

• UseCase diagrams using Poseidon 3.2

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Agenda

• The Tutorial Example
• How to start
• Boundaries/ Actors/ UseCases

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The Tutorial Example

• Board Game System
• Define global preferences
• Choose one of several games
• Chess / Nine Mens Morris /
• play against a human or AI
• save all turns for each game
• validate turns
• restart from a past state
• save/load

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How to start ?

• Find system boundary
• Usually Part of Analyses Phase
• Find Actors
• Find Use Cases

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Boundaries

• MUST have
• SHOULD have
• NICE to have
• System LIMITS
• System is NOT

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Boundaries (2)

• MUST
• Define Player Names
• Choose game
• Make turn/ Undo turn/ Advice turn
• SHOULD
• Stop game
• NICE to have
• choose player color
• SYSTEM is not
• No intelligence, just an interface

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Actors

• Who or what uses the system?
• What roles do they play in interaction?
• Who maintains the system?
• What other systems interact with it?
• Who gets and provides information?
• Do things happen at fixed times?

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Actors

• Player 1
• Player 2
• AI Player
• Time

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Glossary

• Actor Glossary
• explains the actors in detail
• introduces domain terms
• to avoid misunderstandings

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UseCase

• For every role, describe typical interactions
  with the system
• We want to understand the requirements, not model
  the system in detail.

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UseCases

• Player 1
• StartGame
• QuitGame
• PlayGame
• DefineName
• GameTurn
• GameTurnAdvice
• ShowAllPossibleTurns

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UseCases

• Player 2
• PlayGame
• DefineName
• GameTurn
• AI Player
• PlayGame
• GameTurnAdvise
• TurnValidation
• Time
• AutoSave

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• Poseidon hints
• Make several diagrams
• One scenario per diagram
• Use packages

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UseCase Description

• UseCase StartGame
• ID UC 1
• Actors PayerOne
• Preconditions
• Flow of events
• 1. The user starts a specific game
• 2. If there is a saved game of this type
• 1. The system shows a load saved game button
• 3. The game begins to load
• Postconditions The player can start playing
• Alternative Flows The user may cancel the game
  start at any time and what leads back to the game
  selection screen
• Postconditions

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UseCase Description

• Document Structure
• Introduction (Business UseCase)
• System Boundaries
• Use Case Description
• Grouped by Scenarios
• Describe each UseCase

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• Thanks for attention !
• Questions ?

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Task 1 Problems

• Naming of Classes
• Use some coding standard and stay within this
  standard.
• Java Coding Convention by SUN
• http//java.sun.com/docs/codeconv/
• CERN Convention
• http//root.cern.ch/root/Conventions.html
• Validate unknown words
• Witch vs. Which

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Task 1 Problems

• Avoid Multiple Inheritance
• As long as you dont know that your programming
  language will support it
• There are elegant other ways
• Attributes and Methods
• Provide Analyses in a later Design Cycle !!
• Organize yourself !!
• Send result to the correct tutor
• Check if the email address is right
• R3MOVE means that these letters should be removed