ⓘ Software requirements specification


ⓘ Software requirements specification

A software requirements specification is a description of a software system to be developed. It is modeled after business requirements specification, also known as a stakeholder requirements specification. The software requirements specification lays out functional and non-functional requirements, and it may include a set of use cases that describe user interactions that the software must provide to the user for perfect interaction.

Software requirements specification establishes the basis for an agreement between customers and contractors or suppliers on how the software product should function in a market-driven project, these roles may be played by the marketing and development divisions. Software requirements specification is a rigorous assessment of requirements before the more specific system design stages, and its goal is to reduce later redesign. It should also provide a realistic basis for estimating product costs, risks, and schedules. Used appropriately, software requirements specifications can help prevent software project failure.

The software requirements specification document lists sufficient and necessary requirements for the project development. To derive the requirements, the developer needs to have clear and thorough understanding of the products under development. This is achieved through detailed and continuous communications with the project team and customer throughout the software development process.

The SRS may be one of a contracts deliverable data item descriptions or have other forms of organizationally-mandated content.

Typically a SRS is written by a technical writer, a systems architect, or a software programmer.


1. Structure

An example organization of an SRS is as follows:

  • Background
  • Purpose
  • Definitions
  • References
  • System overview
  • Overall description
  • Hardware interfaces
  • Memory Constraints
  • Product perspective
  • Communication Interfaces
  • Software interfaces
  • User interfaces
  • System Interfaces
  • Site Adaptation Requirements
  • Operations
  • Design constraints
  • User characteristics
  • Constraints, assumptions and dependencies
  • Product functions
  • External interface requirements
  • Reliability
  • Specific requirements
  • Functional requirements
  • Software System Attributes
  • Performance requirements
  • Portability
  • Availability
  • Logical database requirement
  • Security
  • Maintainability
  • Functional requirements
  • control description
  • functional description
  • functional partitioning
  • Environment characteristics
  • people
  • peripherals
  • Hardware
  • other

2. Goals

The Software Requirements Specification SRS is a communication tool between users and software designers. The specific goals of the SRS are as follows:

  • Providing a platform for ongoing refinement via incomplete specs or questions
  • Facilitating reviews
  • Including features to customer requirements
  • Providing a framework for testing primary and secondary use cases
  • Describing the scope of work
  • Providing a reference to software designers i.e. navigation aids, document structure

3. Requirements smell

Following the idea of code smells, the notion of requirements smell has been proposed to describe issues in requirements specification where the requirement is not necessarily wrong but could be problematic.

Examples of requirements smells are Subjective Language, Ambiguous Adverbs and Adjectives, Superlatives and Negative Statements.