Software Requirement Specification is the description of the software that has to be developed which contain all the specification that meets the customer needs. This is the plan that are explaining what software will do. This is the most important document to develop the design by providing the basic development design. This will reduce the development effort by following the SRS. This will force various concerned groups of the customer’s organization to consider all the requirements before software go to design. A complete SRS reduces the effort that are waist on redesigning it recode and retest. By describing the SRS of the product that has to be developed is estimating project cost. This will provide a baseline for verification and validation in that organization start do testing from the early phase and start making test documentation which is more productive from a good SRS. Also easy to facilitates which make it easier to transfer product to new user or new machine.
Lets take an example to clear the concept of SRS. A grocery shop record all the transaction on the written ledger, everything from lending the products to recording payment. Now they want to automate the manual process through computerized system. So they handed over this responsibility to a local software company, they are going to maintain the database for them. Before the company writing code, software developers gather out all the specification for automating the components this would be the early stage in development process of software i.e. software requirement specification(SRS) stage.
When the software is developed it need to be test under different levels of testing to make sure that software is designed according to customer specification or not. So in verification and validation model testing is start from the very early phase. Tester will start testing for SRS and once they are approved it will send to developers and they start writing code for it. All the process done on the different phases so that client can change his requirement if he wants to means it is flexible to change client’s requirements. Verification is about are we making product right? Or validation is about are we making a right product?