Page 62 - DCAP305_PRINCIPLES_OF_SOFTWARE_ENGINEERING

Principles of Software Engineering

Notes 3.5.1 Types of Requirements
There are various categories of the requirements. On the basis of their priority, the requirements
are classified into the following three types:
1. Those that should be absolutely met.

2. Those are highly desirable but not necessary.
3. Those that are possible but could be eliminated.
On the basis of their functionality, the requirements are classified into the following two types:

Functional Requirements
They define the factors like, I/O formats, storage structure, computational capabilities, timing
and synchronization.
Non-functional Requirements
They define the properties or qualities of a product including usability, efficiency, performance,
space, reliability, portability etc.
Software Requirements Specification
Requirements specification for a software system is a complete explanation of the behavior of
a system to be urbanized and may include a set of use cases that describe communications the
users will have with the software. In addition it also contains non-functional requirements. Non-
functional requirements impose constraints on the design or implementation (such as performance
engineering requirements, quality standards, or design constraints), and are sometimes referred
to as “ilities”. A software requirement is a sub-field of software engineering that deals with the
elicitation, analysis, specification, and validation of requirements for software. The software
requirement specification document enlists all necessary requirements for project development,
to derive the requirements we need to have clear and thorough understanding of the products
to be developed. This is prepared after detailed communications with project team and the
customer. General organization of a SRS is as follows:
Introduction

• Purpose
• Definitions

• System overview
• References
Overall Description
• Product perspective

• Product functions
• User characteristics
• Constraints, assumptions and dependencies

Specific Requirements
• External interface requirements
• Functional requirements

• Performance requirements

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