Explain << include >> and << extend >> relationships in use case diagram. OR Explain <<include>> and <<extend>> dependencies used in use case diagrams.

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teamques10 ★ 67k

<<include>> relationships: Include relationship is used to include one use case within the behavior sequence of another use case.

An include relationship between use cases means that the base case explicitly incorporates the behavior of another use case at a location specified in the base.
The include use case never stand alone. When an actor initiates any base use case then base use case executes included use case.
An include relationship as a dependency can be render with stereotyped as include. To specify the location in a flow of events in which the base use case includes the behavior of another, write include followed by the name of the use case.
Arrow is placed near the included use case. Arrow is directed from base use case to included use case.

Example:

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<<extend>> relationships: It adds incremental behavior of an use case.

A extend relationship between use cases means that the base use case implicitly incorporates the behavior of another use case at a location specified indirectly by the extending use case.
The extended use case adds itself to the base use case. Most of the time, an extend relationship has a condition attached to it. The extended use case executes only when the condition is true.
The base use case may stand alone, but under certain conditions, its behavior may be extended by behavior of another use case.
An extend relationship as a dependency can be render with stereotyped as extend. Arrow is directed from extended use case towards base use case.

Example:

enter image description here

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