Use-case diagram for payment scenario

Question

I want to clarify one scenario in use-case diagram which involve in payment. There are 2 way of doing a payment.

1. Using card
2. Using mobile number

Here want to clarify about the second one. To do a mobile base payment first user need to add the mobile number when user try to do a payment in payment page. I put that as a extend relationship. Please tell me is this correct.

Answer 1

Formally, this is not correct. Use-cases could be associated with actors but not with other use-cases: the relationship between two use-cases may be «extend», or «include» or specialization. In consequence, Add mobile number and mobile can't be associated the ay you have diagrammed it.

Depending on what you mean, you may correct your diagram:

• by showing that mobile includes Add mobile number (dashed line with arrow), if you mean that every time mobile is executed, add mobile number would also be executed.
• by showing that Add mobile number extends mobile (dashed line with arrow), if you mean that in some cases where mobile is executed, add mobile number could need to be executed as well.

Other notation improvement coulb be to get rid of the arrows for associations wetween actors and use-cases. This is an obsolete notation.

Beyond these purely formal remarks, it's important to realize that use-cases should represent goals of value for users. While we would certainly agree that payment is a goal for the user, and we could certainly understand your desire to add extensions for different payment means, we would certainly not agree on the fact that Add mobile number is a goal for the user. It's either functional decomposition or user-interface details, both aspects that should in principle not be documented in a UC diagram.