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4  Develop   use-  case  scenarios

A detailed 

scenario

 is then developed to detail the different paths of events and activities for 

each  use-  case. The primary scenario describes the typical case where nothing goes wrong. 

The  use-  case includes detail of activities or functions, what happens when there is an alterna-

tive or decision, or if there is an error.  Pre-  conditions for entering and  post-  conditions for 

exiting the  use-  case are also specified.

Figure 11.13 shows a primary scenario for the complete e-commerce purchase cycle. A 

more detailed primary scenario for the particular  use-  case ‘Register’ written from the point 

of view of the customer actor from Figure 11.14 is as follows:

 Pre-  condition: A user is active on the website.

Scenario: Register.

Basic path:

1 

 Use-  case starts when customer presses ‘register’.

2 

Customer enters name, postal address and email.

3 

The post/postcode and email address (@ symbol) will be checked for validity after entry 

and the user prompted if there is an error.