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Asked: 2026-06-19T00:57:07+00:00

Am I allowed to make a use case which does nothing? For example, consider

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Am I allowed to make a use case which “does nothing”? For example, consider a soda vending machine: it can vend a can of soda or a cup of soda.

So my top level use case is “buy soda”. The extending use cases are “buy can of soda” and “buy a cup of soda”. Can I make “buy soda” blank, i.e. it has no steps?

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  1. Editorial Team

    No, because “buy can of soda” and “buy a cup of soda” are extending use cases, and the extend relationship requires at least one ExtensionPoint from the extended use case. (UML Superstructure v2.4.1 section 16.3.3). An extension point is a reference to a location within a use case at which parts of the behavior of other use cases may be inserted (section 16.3.4).

    In other words, you have to specify how and when the behaviors defined in “buy can of soda” and “buy a cup of soda” can be inserted into the behavior defined in “buy soda”.

    There is a similar example in the standard (Fig 16.3), which I adapted to your use cases. See: http://tinypic.com/r/huisg3/6

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