How to Create Software Requirements Specification (SRS Document): A Guide

by Anand Suresh

Today’s software market is awash with products of all molds and builds, each claiming to be better than the rest. In such an environment, where competition is stiff and customers are hard to come by, how do you create an unrivaled software product that gives you an edge over the competition? The answer lies in doing the little things right. You might have a truly unique software idea but the journey to take it to the implementation stage ultimately decides whether your product will succeed or flop. A Software Requirements Specification (SRS document) is a vital part of this journey. It acts as a roadmap, guiding your software team through the entire process of application development from start to finish. Explore the essentials of this document and discover the steps that can help you create software requirements specification documentation for successful product implementation in this blog.

What Is a Software Requirements Specification (SRS) Document?

An SRS (software requirements specification) is a document that details the functional and non-functional specifications for a future software system—along with additional information about the surrounding project.

The overall goal of an SRS is to communicate to the software development team: 

  • How the software should be developed
  • How it should work (often complimented by use cases)
  • The software’s intended purpose, features, and behavior

SRS documents are typically written by software or project managers, who do user research or who directly communicate with clients and gather future product requirements. However, all stakeholders involved in the creation process ensure the document is clear, coherent, and comprehensive—and that it will help get the development team started on the right foot.

Bonus

Download a PDF version of this Checklist. Access it offline anytime. Bring it to team or client meetings.

Why Should You Create One?

SRS Document

An SRS document is vital, particularly when you’re working with an external team to develop your software application. It ensures you cover all the necessary details about the software and exactly how you want it to turn out. This means that the software development team will have a clearer picture of what you’re trying to accomplish, leaving little room for guesswork or flaws. An SRS document almost guarantees that the vision you have in your head and the finished product match.

In addition to being a developer’s detailed guide to building your software, an SRS document can also help get all the stakeholders aligned and create a shared understanding. Successfully delivering a software product requires the collaboration of multiple teams, including project managers, testers, designers, and developers. An SRS sets the course for the release, keeping all contributors in sync and ensuring that the project finishes on time and within budget. 

How Is It Different From a Product Requirements Document?

Generally speaking, where there is both a product requirements document (PRD) and a software requirements specification (SRS) document, the PRD contains high-level product requirements, whereas the SRS provides execution-level detail on the implementation of the requirements. In other words, a PRD answers the what of a software project, while an SRS answers the how.

The PRD will usually define the target market and provide a prioritized list of customer requirements the product will need to satisfy to be successful. This shapes the list of core capabilities described in the SRS.

How to Write an SRS Document

While these documents are relatively straightforward, creating an SRS document is still an involved and intensive process that can quickly go off-track if you aren’t careful.

So, you need to approach the creation of your SRS strategically and methodically to make the most of it.

Here’s what the structure should look like.

Introduction

What’s the Purpose of the Product?

Start your SRS by outlining the purpose of the product you are developing. All stakeholders need to be firmly aligned on it. You can summarize this section by answering three key questions:

  • What problems does this software solve?
  • Who will use this product?
  • Why is it important?

Who’s the Intended Audience?

The “audience” you’re defining here is not the product’s end-users, but rather, those who’ll read your SRS. Different parts of your SRS are meant for different readers. Make that clear in this section. For better clarity, including a list of all the relevant stakeholders as well, from developers to testers and everyone in between.

Scope

What are the goals, benefits, and objectives that you intend to have for your product? Neatly outline them here, and make sure they relate to overall business objectives. This is particularly crucial if teams outside of development will have access to the SRS. 

General Description

Product Perspective

Here’s the part where you explain the app’s idea, where it came from, and why it can be interesting for users.

Product Features

This section will provide a high-level outline of the product’s functions and features. Every feature you highlight here needs to be driven by the purpose you outlined in the previous section. 

User Class and Characteristics (User Needs)

Once you’ve fleshed out your product’s features, the next step is to identify and analyze the customers who will be using it and how. List all the possible ways your audience can use your product based on a set of predetermined classifications i.e. age, gender, job roles, purchasing behavior, and so on.

Defining and categorizing end-users is a huge help in understanding what they would like and what they won’t. It also allows you to know features they would take positively and how they would be using your product.

Operating Environment

Be sure to describe the digital or physical space where the software will exist. For instance, if this is a cloud-based app, it’s vital to specify which cloud application development services are necessary. If instead, the app exists as part of an ongoing software application development endeavor, you’ll want to be clear on the kind of devices that are required to use it.

Constraints

Constraints are the limitations in place that prohibit your team from “doing more” in a certain regard. Common constraints include budget, time, and access to resources. Risk is another technical constraint, as it can inhibit development breakthroughs in the interest of “playing it safe.” Whatever constraints you envision down the road, lay them out in this section.

Assumptions & Dependencies

You’ll also want to list out any assumptions and/or dependencies that exist within your plan. 

Assumptions refer to any expectations you have about the project, the user, your developers’ capabilities, etc. For instance, you might assume that your development team is fully trained to use a certain tool, or that your target user has a certain level of expertise.

Dependencies, on the other hand, define the limitations and relationships between development tasks. Beyond making these limitations known, defining dependencies also allows you to plan around specific tasks whenever possible.

System Requirements

This is the most important section of the entire document. You’ll want to elaborate on the product’s functional and non-functional requirements down to the last detail.

Functional Requirements (FRS)

Such requirements describe system behavior under different conditions and user scenarios. They pinpoint what your app development team must do to make it easier for users to accomplish their tasks.

The best way to nail this section is to ask yourself: “Does this add to my app’s functionality?” or “What function does this provide?”

Here are a few examples of functional requirements:

  • Business rules
  • Transaction corrections, adjustments, and cancellations
  • Authentication
  • Administrative functions
  • Historical data
  • Audit tracking
  • Certification requirements
  • Reporting requirements

Much as this may look like a lot, try not to leave out any requirement that you think should be in there. The more elaborate and detailed your SRS is, the less correction you’ll need to do later on.

External Interface Requirements

This section will break down what APIs to use, how interfaces will communicate with each other, how the system collects different types of data, etc. These types of requirements have four subcategories, each covering different types of interface interactions:

  • User interfaces: Here, you’ll want to clearly describe the relationship between the user and the system. 
  • Hardware interfaces: This subparagraph must deal with the interaction between software and hardware components.
  • Communication interfaces: In this subsection, you’ll highlight the communication channels used by the system such as browsers, emails, e-forms, server protocols, and others.
  • Software interfaces: This part is about the correlation between software and its components such as databases, OS, libraries, etc.

Non-Functional Requirements (NFRs)

The final step in your SRS creation journey is to detail your product’s non-functional requirements. These are quality attributes that describe the ways your system should behave. Unlike functional requirements which tell a system what to do, non-functional requirements describe how your software will implement these features.

NFRs are often thought of as the “itys.” While the specifics will vary between systems, having a list of these NFR types defined up front provides a handy checklist to make sure you’re not missing crucial requirements. 

This is not an exhaustive list, but here’s what we mean:

  • Security: Does your product transmit or store sensitive information? What security best practices are used in your industry?
  • Capacity: What are the minimum hardware requirements? What operating systems and their versions must be supported?
  • Reliability and availability: What is the critical failure time under normal usage? Does a user need access to this all hours of every day?
  • Maintainability and manageability: How much time does it take to fix components, and how easily can an administrator manage the system?
  • Scalability: The Black Friday test. What are the highest workloads under which the system will still perform as expected?
  • Usability: How easy is it to use the product? 

Other common types of non-functional requirements include regulatory, performance, and environmental.

Should You Use Google Docs/Microsoft Word or Other Software?

SRS Document Guide

Google Docs and Microsoft Word are both good choices for writing your software requirements specification document. A smart way to do this is to create a standard SRS template, which you can use as a starting point for current and future projects. We’ve already done that for you here.

However, keeping an SRS document up-to-date with Microsoft Word or Google Docs can be hard at times, especially if your project’s scope is extensive. It’s harder to collaborate. And it’s nearly impossible to be Agile.

That’s why some development teams opt to use requirements management software or knowledge base system to bring their SRS idea to life. It keeps them away from siloes of information. On top of that, requirements are always up-to-date. 

What Happens After Writing an SRS Document?

Upon the completion of your SRS, you’ll want to ensure that all relevant parties can access it at their convenience.

Throughout development, all stakeholders will need to refer back to the SRS and other related documentation to maintain focus and alignment. If and when need be, teams may also add artifacts, data, and information to certain sections of the document to make it more comprehensive.

Once the project is complete, the accompanying SRS should then be stored more permanently within your archives. From there, teams can retrieve it for different purposes, such as:

  • Crafting an SRS for a related but separate software
  • Preparing an SRS for a future software iteration
  • Assessing your team’s performance and processes

Final Thoughts

If you faithfully plowed through the information above, you’re well on your way to creating a stellar Software Requirements Specification document. While it can take a little time upfront, the benefits are worth the effort, and our example template should help you start.

We’re a team of budding product people (just like you!), so if you found this article helpful, feel free to check out the rest of our blogs. Also, if you would like to be at the forefront of enterprise digital transformation and ultimately unlock new potential for your workflows and infrastructure, talk to us today. In this day and age, going from traditional to digital is not enough; let us show you why.

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