A software requirements specification (SRS) is a description of a software system to be developed, laying out functional and non-functional requirements. (Non-functional requirements impose constraints on the design or implementation such as performance engineering requirements, quality standards, or design constraints.) The specification may include a set of use cases that describe interactions the users will have with the software.
Software requirements specification establishes the basis for agreement between customers and contractors or suppliers (in market-driven projects, these roles may be played by the marketing and development divisions) on what the software product is to do as well as what it is not expected to do. Software requirements specification permits a rigorous assessment of requirements before design can begin and reduces later redesign. It should also provide a realistic basis for estimating product costs, risks, and schedules.
The software requirements specification document enlists enough and necessary requirements that are required for the project development. To derive the requirements we need to have clear and thorough understanding of the products to be developed or being developed. This is achieved and refined with detailed and continuous communications with the project team and customer till the completion of the software.
One of the main values of writing specifications is to have them reviewed by stakeholders and to allow the stakeholders to provide feedback. Therefore, specifications should be written in such a way that they can easily be read and reviewed.
Some of the questions to ask yourself about readability is:
Does the specification contain a high-level description of the scope of the work?
Does the formatting allow a reader to easily navigate the specification?
Does the formatting allow a reader to easily understand the primary versus secondary cases?
Does the specification contain links to related features?
Does the specification call out questions which still need to be addressed?