Explain Requirements modeling ?

Requirements modeling is important activity to ensure the consistency and completeness of the requirements. It is carried out after the requirements and constraints for an area have been captured and analysed. There are multiple ways to model functional, quality attributes and constraints. The appropriate approach to take will depend on the type of system and the organizational standards, in some cases they are domain specific modelling languages which are used.

Requirement modeling strategies :

1. Flow oriented Modeling :

The flow oriented modeling shows how the data objects are transformed by processing the function. The elements of flow oriented modeling are as follows :

a. Data flow model : The data flow model is graphical technique which is used to represent information flow. in data flow model the data objects are flowing within the software and transformed by processing the elements, the data objects are represented by labeled arrows. Transformation are represented by circles called as bubbles. And DFD shown in a hierarchical fashion. The DFD is split into different levels. It also called as 'context level diagram'.

b. Control flow model : The large class applications require a control flow modeling. In control flow model application creates control information instated of reports or displays and the applications process the information in specified time. An event is implemented as a boolean value. For example, the boolean values are true or false, on or off, 1 or 0.

c. Control specification : The control specification represents the behaviour of the system. The state diagram in control specification is a sequential specification of the behaviour. The state diagram includes states, transitions, events and activities. State diagram shows the transition from one state to another state if a particular event has occurred.

d. Process specification : The process specification is used to describe all flow model processes. The content of process specification consists narrative text, Program Design Language(PDL) of the process algorithm, mathematical equations, tables or UML activity diagram.

2. Class-based Modeling :

Class based modeling represents the object. The system manipulates the operations. The elements of the class based model consist of classes and object, attributes, operations, class – responsibility - collaborator (CRS) models.

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