- Use Case Modelling

Their are three types of use cases:


              Primary Uses Cases are directly invoked by an actor when they  instigate the beginning of a new use case.  


The other two types are invoked by another use case.

                 'Included' Use Cases come into use when another use case, that is already running, decides that  the 'included                                                                use case' should be run.

                                                             For example; a computer guiding a medical doctor through a series of questions  to ask a

                                                             patient, should skip 'genealogical' questions if the patient                                                                         

                                                             In some cases, the calling use case always uses an <<included>> use case, because it just                                                              needs to 'share' it with other use cases.


                 'Extended' Use Cases come into use when another use case, already running, decides that the 'extended use case'                                                  should be run, but only if the assistant agrees.

                                                             For example; the same computer is guiding a doctor through a series of questions but the doctor

                                                             may not want to discuss questions on 'cancer' in the current session.