Essential Software Requirements

Prof M L Saikumar

Institute of Public Enterprise

HR Manager VS SW developer

Role Play

The Essential Software Requirement

• Customer side– How frustrating it is to use a software product

• Developer side– How frustrating it is to learn of functionality the

user expects only after the system has been implemented

– Annoying to have your current project interrupted

– Modify a system that is doing precisely what you were told it should do in the first place.

• Between 40 and 60 percent of all defects found in a

software project can be traced back to errors made

during the requirements state

Leffingwell, Dean, “Calculating the Return on Investment from More Effective

Requirements Management”. American Programmer 10(4), 1997: 13-16

Interpretations of “Requirements”• A key concept is that the requirements must be

documented• The statement of needs by a user that triggers the

development of a program or system.

Davis,. Alan M Software Requirements: Object, Functions, and States

PTR Prentice Hall Englewood Cliffs, NJ, 1993.

• A user need or a necessary feature, function, or attribute of a system that can be sensed from a position external to that system

Sommerville, Ian, and Pete Sawyer., Requirements Engieering: A Good Practice Guide.

Chichester, England: John Wiley & Sons, 1997

Levels of Requirements

• Software requirements include three distinct levels- business requirements, user requirements and functional requirements

• Business requirements represent high-level objectives of the organization

• User requirements describe tasks the users must be able to accomplish with the product

• Functional requirements define the software functionality the developers must build into the product.

Relationship of several components of software requirements

BusinessRequirements

Vision and Scope Document

UserRequirements

FunctionalRequirements

Use-Case Document

Constraints

QualityAttributes

OtherNonfunctional Requirements

SystemRequirements

Software RequirementsSpecification

Risks from Inadequate Requirements Processes

• Insufficient User Involvement

• Creeping User Requirements

• Ambiguous Requirements

• Unnecessary Features

• Minimal Specification

• Overlooked User Classes

• Inaccurate Planning

The Boundary between requirements development and management

Marketing Customers, Management

Analyze,Document,

Review,Negotiate

RequirementsChangeProcess

requirements

Base lined Requirements

RequirementsDevelopment

RequirementsManagement

Currentbaseline

revisebaseline

requirements

changes

project

changes

Marketing,Customers,Management

ProjectEnvironment