Use Case Descriptions and Preconditions

Use Case Descriptions

• Use case descriptions consist of interactions among a product and an actor.
• A use case description includes the use case name and number, actors, and stakeholders and needs.

Preconditions and Postconditions

• A precondition is an assertion guaranteed to be true before the activity or operation begins.
• A postcondition is an assertion guaranteed to be true when the activity or operation finishes.

Triggers

• A trigger is an event that causes a use case to begin.

Use Case Description Format

• Underline text refers to another use case.
• Extensions section uses complicated numbering scheme.
• Indentation is used to make extensions easier to read.

Methods of Writing Use Case Descriptions

• Actors in a use case are almost always stakeholders.
• Preconditions must be true before the statement begins.
• Need list should be reviewed when writing each use case.

Extensions

• Once the basic flow is defined, the extensions can be specified.
• The alternatives are called extensions as they extend the activity flow in a different direction from a branch point.

Use Case Description Heuristics

• Fill in the use case template from top to bottom.
• Write simple declarative sentences in active voice.
• Avoid sequence of steps by the actors and product.

Alternative Use Cases

• A different alternative must consist of different overall product functionality.

Use Case Diagrams

• Interactions supported by a product are cataloged in a use case description.
• Interactions are refined in a use case diagram.

Use Case Driven Iterative Development

• At each iteration, one or more use cases are selected for implementation.
• Iteration should be followed until the system is complete.
• Iterative development builds system functionality gradually through analysis, design, coding, testing, and evaluation.

This quiz assesses knowledge of use case descriptions, including interactions, contents, and preconditions. It covers the relationships between products, actors, and stakeholders, as well as the structure of use case descriptions.