Use Case Modelling

Question 1

What are Use Cases?

Answer 1

• Describe the sequence of events to yield a result
• Considers flow to/flow from the system and possible outcomes, including failure

Question 2

What is an Actor?

Answer 2

Someone or something external to the system that interacts with it
- Human user, a role not a person
- Can be another system

Question 3

What is a Use Case?

Answer 3

An activity that the system carries out in response to a request from an actor
- A way in which a user may interact with a system
- An action undertaken on a system to achieve a goal

Question 4

What should a proper Use Case include?

Answer 4

Capture
- Who (actor) does
- What (interaction) with the system
- For what purpose (goal)

Question 5

What should a complete set of cases do?

Answer 5

• Specify all the different ways to use the system
• Define all the behaviour required of the system

Question 6

What is the use of Use Case index and what is included?

Answer 6

• A list of all use cases is kept in an index
• Helps to organise and manage cases
• ID, Name, Primary Actor, Complexity and Priority

Question 7

What is a Use Case diagram?

Answer 7

• A simple diagram showing a high-level overview of all use cases
• Models all functionality of a system from the users’ point of view
• Shows how actors interact with the system
• No detail given about steps within use cases
• Good for communicating with stakeholders

Question 8

What is the use of Textual Use Cases?

Answer 8

• Helps to understand all the steps involved in a use case
• Level of detail can be increased or decreased as needed

Question 9

What are the 3 sequences in a Textual Use Case?

Answer 9

• Happy path: when things go right
• Unhappy path: when things go wrong, AKA exception conditions
• Alternate flow: different path taken