Requirements and Design:
Requirements are basically the need. But we often end up giving the design in the Requirements.
Requirements are specifically an external visible function or an attribute of a system.
Well, this shall give an clarity on what is the prime difference between the Requirements, Design Documents and the Business case.
Business case Requirements:
If we need an External visible function then the Requirements document doesn’t talk about the objective and aims.
The goals and objectives are mentioned in the Business case, these are always validated against the Requirement Documents.
Business case talks about the opportunities and the challenges.
Business case is all about the aspirations of the system.
The misconstrue is with requirements is that they should not design the documents.
Requirements Document is all about how the functionality of the system should work.
The functionalities how a system should work.
This has the External Interfaces, Functions and Logical Data bases.
External Interfaces : Describes the logical levels in a database :
Purpose of the screens
Allowable ranges of data
Everything about the In and out of the system
What the system should logically perform, with:
Inputs used and outputs produced
The logical requirements are:
Types of information held
Things not included in the Requirement are the design documents.
Physical aspects on how a system is built
How the functions splits code modules
Interfaces between the modules
Physical database structure.
Design documents involves in the physical design of the system.