When we writing a use case scenario what should I do if there is an extention point?

Question

When we writing a use case scenario for base use case if there is included use case (include relationship), We are including it in Basic Flow of Use case scenario. ex :-

UC name : Pay Bill 
Actor : Customer
Basic Flow :  1. Include ::( Validate User Login).
              2. Press View Unpaid bills button.
              3. System show list of unpaid bills.
etc...

What if there is an extend relationship with extension point? Where should I mentioned it on use case scenario ?

Yes, with extends. But it's not "nominal" scenario. – Weenesta - Mathieu Dormeval Mar 22 '17 at 08:30 — Weenesta - Mathieu Dormeval, Mar 22 '17 at 08:30

score 0 · Accepted Answer · answered Mar 22 '17 at 08:57

0

An <<extends>> relation is just like an (unconditional) <<include>> except that it is bound to some condition. So you can write it the way you did.

answered Mar 22 '17 at 08:57

qwerty_so

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Write in where ? in basic flow ? or in alternative flow ? – Samith Dilshan Mar 22 '17 at 14:15
I guess you guessed it ;-) Of course it will be in a conditional part of the flow which can be either in the sunny day or any alternative scenario. It's just that the extends is a conditional include. – qwerty_so Mar 22 '17 at 19:47

score 0 · Answer 2 · answered Mar 22 '17 at 15:54

The basic flow lists steps that happens most often when performing UC. You do not put there any options. The assumption is simple - if everything is ok, you go through steps described in basic flow.

Any deviation (even if also happening quite often) are placed in alternative flow. You only list steps that are different than the basic flow. Your alternative flow starts with a condition when it is triggered that is followed by steps of alternative flow. Last step might be either some kind of whole flow end or a return to a basic flow (not necessarily in the same place you left it).

Alternative flow again depicts only one possible flow. If further deviations are possible, they will pose new alternative flows (done might be alternative to alternative).

Note that alternative flow does not automatically mean you have extension to your UC (on the contrary, straight from the definition you'll have multiple possible flows in one UC and only on a very rare occasions some of them will show some extending UC).

In your case you might have alternative flow as follows:

3a No unpaid bills

    3a1 System shows pop-up message "No unpaid bills"
    3a2 User clicks OK button
    3a3 System returns to main screen

When we writing a use case scenario what should I do if there is an extention point?

2 Answers2