Modelling Requirements -USE CASE

                                                                     Modelling Requirements

                In modelling requirements, we use different techniques for IT systems. These techniques are used to analyse and specify requirements during the developing the system according the requiremens.

                Models are very helpful to clarify ,understand and cross check the requirements. For completeness of the analysis. These models are perspective of system and users. For that purpose we use Unified Modeling Language and Entity relationship modelling(Data driven model).

Modelling system requirements

                                                            “One picture worth 10,000 words”

                      Its extremely difficult, If not impossible, to write textual statements thar are completely umambiguous.

The view of a system that is often most accessible to business users depicts the funtions that will be provided and the actors who are involved in using those functions.

                A function may be defined as a set of actions that the business users want the IT system to support in order to achieve a specific goal.

·         Accepting the details of the customer

·         Validate the details

·         Store the customer details to retrieve and filter details according to our specifications.

Unified Modelling language

                                               In UML, a use case is something that an actor wants the IT system to do; It is a Use case of the system by a specific actor and describes the interaction between the actor and the system.

Each use case has specific task and description to support the functional and non functional requirements and how user and system interacts.

                                                                         USE CASE 

          

Commonly we found in the use case diagram are

·            Actors

·            Use case

·            System Boundary

·            Associations

Actors :  Actors are the users of the system who access the functionality of the system i.e Use case of the systems.

                   Actors are 2 types

·         Primary actors : who are the directly interacting with system and access the functionality of the system

·         Secondary actors : Most of the time, Back end operators like data bases and supporting members come into this category.

Use case :

                  Is shown as an oval and represents a function that the system will perform in response to a trigger from the actor.

System boundary

                 Is indicated by drawing a large box around all of the use cases but with the actors outside the box.

Associations

              Indicate which actors will need to interact with which use cases. Lines are drawn linking actors with the appropriate use cases.

v  Generalization

                     USE case generalization

                                                                                             Actor Generalization                                        

v   INCLUDE

v   EXTEND