Writing Effective Software Requirements

Effective software requirements shouldn’t be taken for granted at all. As effective software requirements save time and money.

Requirements describes what features a software should include and how these features should work and often described in a document.

A software requirement document (SRS) simply defines everything that the software should accomplish, emphasis on should. Which means bad requirements, requirements that were not detailed enough, requirements that were not captured are devastating and costly mistakes.

There can be several types of requirements in software development for example

Business Requirements

  • These are high level requirements that should help achieve a business goal. For example, a pet grooming service needs to increase their customer bookings by providing an online solution.

Architectural and Design requirements

  • These requirements are much more detailed in nature than business requirements. It determines the overall design required to implement the business requirement.

Software Requirements

  • Functional – Requirements that represent what the system should do.
  • Non-functional – Requirements that represent how the system should do it.

We can define more categories as we like, however, how we approach them is what’s important. Writing good software requirements takes skill, practice, and patience.

This article explains the importance of writing good software requirements and how to write effective software requirements and the best practices to consider when doing so.

Why Are Software Requirements Important?

A good software requirement specification (SRS) provides clear communication of the software to be built to the stockholders on what is being developed and how it will function. Creating an SRS is as an invaluable document when developing new software. The importance of software requirements is best understood by quality assurance specialists (QA). When project requirements are not laid out properly, QAs receives the bad end of the deal. Imagine trying to determine whether or not a software feature works if there is no clear specification on what it should do and how it should do it. I think that’s madness.

Some of the goals of software requirement specifications include:

  • A description of the work to be completed
  • Easy and clear details for software developers and designers
  • Includes stockholder’s input
  • Provides use case scenarios for the development team
  • Verify the alignment with customer requirements to features

Benefits of Effective Software Requirements

The SRS saves valuable time in providing a communication tool throughout the development process, even when a new developer has been added to the team. In addition, a comprehensive SRS will:

  • Act as a single source of truth
  • Increase the accuracy of cost and time estimates
  • Reduce development effort
  • Improve the quality of work
  • Provide future reference for documented details

Best Practices for Writing Effective Software Requirements

Now that we have an understanding of what requirements are and why we need them let’s look at how we can write better software requirements.

Let us consider the example of a pet grooming system where customers can make reservations to come in and groom their pets.

The requirements for this system must maintain a standard quality. These requirements should be:

  • Atomic
  • Uniquely identified
  • Complete
  • Consistent
  • Prioritised
  • Testable

Atomic

Atomic, (of a substance) consisting of uncombined atoms rather than molecules. Atomic, of or forming a single irreducible unit or component in a larger system.

By looking at the definitions above we can actually get an idea of what it means to be atomic but if that is not clear enough. Let us say, Atomic requirements should be at a very low level of detail. It should not be possible to be separated out into other requirements.

For example, customers should be able to select the date and time for which they want to make a booking.

The requirement above is not the best requirement because it can be further broken down into multiple requirements.

Customers should be able to select the date….

Customers should be able to select the time….

Here we see that we were able to create two additional requirements. Trivial but you get the idea.

Uniquely identified

The next quality to introduce would be for the requirement to be uniquely identifiable. It should be possible to talk about a requirement based on a reference id versus trying describe the requirement itself. That way we can have better tracking of requirements.

1. Customer Booking

1.1 Customers should be able to select the date….

1.2 Customers should be able to select the time….

Here we can clearly identify each requirement with a reference number. This makes recollection of the requirements much easier and help avoid mistakes.

Complete

Each requirement should be complete. For example:

The customer should be able to select the type of animal, gender and other information…

The requirement above is not necessarily a good one because it is not complete. It includes ambiguous information when we introduce the words “other information”. A better requirement would be: The customer should be able to select the type of animal, gender, height, age and any illnesses. This requirement represents a complete one that removes any ambiguity. Everything is complete and spelt out.

Consistent

Requirements must not contain conflicting requirements. User needs to make a trade-off decision in case of conflicts. The requirements should be consistent with each other so as to provide clarity.

Prioritised

Each requirement must be prioritised, after all if everything is important, nothing is. The team needs to have clear guidelines on which requirement should be done and implemented first. Often times the development methodology usual have a say in how this is done, ie. Agile or waterfall. Whichever methodology is chosen we can still reach a point where requirements need further prioritisation.

Testable

Requirements should be testable. Which ties back to why the standards from above needs to be implemented in requirements. Requirements needs to be specific because testing needs to be specific. A bad requirement is “each page should load in an acceptable time frame”. Can you guess the problem here? What exactly is an “acceptable” time frame? 2s, 2mins, 2 days. Imagine a page taking a day to load my gosh, just enough time to buy a gun and shoot myself with it, please! So we have to ensure our requirements are testable. So our requirements should tell us about which page, and exactly what time frame based on industry standards in a particular area.

Conclusion

With these newly formed superpowers I hope we can get a better understanding of how to create quality software requirements. At the very least, bring some reminder and mindfulness when doing our analysis of software requirements.

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