Difference between Uses and Extends


 Difference between Uses and Extends

Probably the best way to think about these diagram elements is as follows:-

"X uses Y" indicates that the task "X" has a subtask "Y"; that is, in the process of completing task "X", task "Y" will be completed at least once.

"X extends Y" indicates that "X" is a task for the same type as "Y", but "X" is a special, more specific case of doing "Y". That is, doing X is a lot like doing Y, but X has a few extra processes to it that go above and beyond the things that must be done in order to complete Y.

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