How to document software requirements without hating your job

Software requirements specifications explain, in painstaking detail, what is expected of a project. So, why develop without one? It's not worth the risk. Read why an SRS is vital.

Good software doesn't appear out of thin air. Even the most experienced Agile development teams must document software requirements to know precisely what they will build and how it should work. Suitable documentation details every key aspect of the product before developers write a single line of code.

A software requirements specification (SRS) is one of the most meaningful and comprehensive software development documents. No enterprise should entrust a vital software project to developers based solely on a verbal discussion or a casual outline. At best, the result would lack essential features and performance levels. At worst, the build wouldn't operate at all in the target environment.

When prepared properly, an SRS gets developers and their customers on the same page, accurately describes what the customer wants and sets a foundation for testing and validation. Typically, an SRS is an extremely comprehensive, formal document of software requirements. Let's look at the major benefits of all that work.

Goals and benefits of an SRS

No engineer constructs a circuit without a schematic, and no contractor builds a home without drawings. By the same logic, no dev and test team should write software without an SRS -- a blueprint of the intended product. The SRS should follow a reasonably standardized and well-developed model for a complete and unambiguous design document that describes precisely what the customer wants and what the developers should provide.

While there is no single rule for how to document software requirements with an SRS, many documents align with the IEEE standard 830-1998.

A well-written SRS enables developers to design and build a product with the assurance that the work will meet the customer's requirements. If it doesn't, however, the SRS helps identify where the product falls short and what requirements to modify. Because the SRS documents software requirements, features and functions, it offers a tangible preview of each build's testing and validation demands. With an SRS, developers can assure customers that the product meets behavior, performance, compliance and security expectations. More important, developers can know when the project is done and avoid costly scope creep or redesign.

Customers must decide upfront precisely what they want in a software product and keep in mind the features, runtime environment and objective measurements of completeness, such as performance and other metrics. Developers can understand exactly where their software will operate, how it should work and any prevailing constraints. Developers should review the SRS for errors and omissions before they start to code, which helps ensure fewer problems or flaws.

In all, a well-written SRS often speeds the development process and lowers costs compared to forging ahead without SRS documentation, yet still results in better quality software. An SRS forms the foundation of any agreement between developers and customers, and it is absolutely critical for contract-based development and test.

Examples of SRS benefits

A clear SRS provides a foundation for either bids from outsourcing providers and consultants or internal development cost estimates.

Let's consider a bank that needs an operational platform for its many branch offices. This platform must perform a comprehensive set of functions that the bank requires, meet the scrutiny of security and applicable financial regulatory compliance and operate within the hardware that exists in the bank's data center. It's virtually impossible for any developer to understand these diverse and detailed criteria without a detailed discussion with the customer. The SRS codifies these understandings.

For outsourced product development, use an SRS to differentiate between competitive bids. In theory, every SRS for prospective outsourcing partners should be the same; the customer has the same requirements, no matter how many developers bid on the work. But, aside from the bottom-line price, the details of an SRS can help a customer select one developer over another.

One developer, for example, might offer UI mockups based on the project owner's requirements and show how the new design improves flow. Similarly, a developer can outline application architecture suggestions for improved cost-efficient scalability on unpredictable or highly variable compute loads.

Without an SRS to document software requirements, a project will likely result in an enormous waste of time, effort and money; developers can't deliver a viable product by agreed dates, and customers won't meet their own roadmap for change and growth.

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