extends vs include in usecase [duplicate]

This question already has answers here: What's is the difference between include and extend in use case diagram? (20 answers) 开发者_运维知识库 Closed 4 years ago.

what is the difference between extends and includes in usecase UML?

if I hava login usecase and and addGroup usecase, the admin should login to be able to add group , what is the relation here??

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One means it is done in the context of of another (almost like a function call) and the other means it is done as an alternative as another. Be careful, they are not using 'extends' and 'includes' in the same manner as OO programming languages. There are subtle differences. I don't remember which is which and would rather not guess.

In all my years of using UML, I still have not come across a situation where either term provided any benefit to a Usecase Diagram.

Here is a page that discusses Extends and Includes in a Usecase Diagram.