CS3340: Intro OOP and Design |
||||||
|
UML- Use Case
Describe how a system interacts with its environment: typical interactions involving its users.
Use Case = goal-oriented collaboration between a system and an actor
Actor = a user adopting a particular role.
Agent = like actor
Action = any goal-oriented collaboration, activity, task, operation or job connecting agents in a business, system or project.
Use-Case description
name goal
The goal represents its specification: the result(s) it achieves, and/or a condition that it maintains.
participants parameters
the objects involved (actively or passively) that are different from one occurrence of the use case to another.
pre-condition (optional)
a statement defining under what conditions the use case makes sense.
post-condition (optional)
a statement defining changes after use-case executed.
NOTE: Can use UML's Object Constraint Language (OCL) to format these description fields
Example: Use-Case Diagram and Description
use case: buy_thing
participants: (Purchaser, Vendor, Thing)
pre-condition:
- vendor.possessions -> includes thing
- purchaser.pocket >= thing.price
post-condition:
- vendor.possessions = vendor.possessions - thing
- purchaser.possessions = purchaser.possessions + thing
- vendor.till = vendor.till@pre + thing.price
- purchaser.pocket = purchaser.pocket@pre - thing.price
