Systems Analysis Chapter 7 Use Cases

Use case diagram

A picture showing system behavior along with the key actors that interact with the system. Represents complete functionality.

Temporal event

A system event triggered by time. The actor is time.

Connection

An association between an actor and a use case. Depicts a usage relationship. Connection does not indicate data flow. Actors are connected to use cases with lines. Use cases are connected to each other with arrows.

Written use case: trigger

An event or action that initiates the use case.

Written use case: stakeholders

Any group or individual with an interest in the function of the use case.

Extend relationship

Association between two use cases where one adds new behaviors or actions to the other. Adds a new behavior or actions. Specialized use case extends the general use case.

Include relationship

Association between two use cases where one uses the functionality contained in the other. Indicates a use case that is used by another use case. Links to general purpose functions, used by many other use cases.

Written use case: precondition

Conditions that must be satisfied in order to execute the use case.

Use Case

Depiction of a system's behavior or functionality under various conditions as the system responds to requests from users.

Written use case: main success scenario

Description of sequence of interactions between actor and use case during the use case execution.

Written use case: title

Descriptive name, matches name in use case diagram.

Written use case: extensions

Detailed description of how errors are handheld.

Written use cases

Document containing detailed specifications for a use case. Contents written as simple text or in a specified format. Step-by-step description of what must occur in a successful use case.

Actor

External entity that interacts with the system. Represent user roles. One user may play many roles, and an actor may represent many users. Not a role, an individual.

System boundary

Includes all relevant use cases. A boundary is the dividing line between the system and its environment. Use cases are within the boundary. Actors are outside. Represented by a box.

Abstract use case

Is when a use case is initiated by another use case.

Written use case minimal: guarantee

Outputs that can be expected if the service attempt failed.

Written use case: guarantee

Outputs that can be expected of the service succeeds.

Abstract use case

Reduces redundancy in two or more other use cases by combining common steps found in both. Depicted as arrow beginning at original use case and pointing to use case it is using.

Association

Relationship between an actor and a use case in which an interaction occurs between them. Modeled as a solid line connecting the actor and use case. Arrowhead indicates a receiver actor.

Depends on

Specifies which other use cases must be performed before the current use case. Depicted as arrow beginning at one use and pointing to use case it depends on.

Extension use case

Steps extracted from another use case to simplify the original. Extends the functionality of the original use case.

Use case

Subset of the overall system functionality. Represented by a horizontal ellipse with name of use case above, below, or inside the ellipse.

Written use case: primary actor

Usually a user role