A software requirements specification (SRS document) describes how a software system should be developed. Simply put, an SRS provides everyone involved with a roadmap for that project.
It offers high-grade definitions for the functional and non-functional specifications of the software, and can also include use cases that illustrate how a user would interact with the system upon completion.
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Suppose you want to create a chat app with a specific appearance and functionality and would like it to be geared specifically to enterprises. You feel that you can cut out the extra features that commercial chat apps use to appeal to the public and focus on features that enterprises need. But you aren’t a developer.
So you need to outsource the development of the app. But you also need to make sure that whoever you hire to turn your idea into reality knows exactly what you’re trying to accomplish. Without all the details to finish the app, time and cost can quickly get out of hand. Developers can take a wrong turn and have to refactor the code if the finished product doesn’t match the picture you had in your head.
An SRS document forces you to put the idea down on paper to cover all these details. You must translate this idea into a language that developers understand. An SRS document describes what a client wants and what developers will provide. It is the written agreement on every detail of the app.
Having a clear set of requirements ensures that a development team creates software that meets the clients’ needs. An SRS will help with estimating the cost of work and covering the project scope. It also gives coders an idea of the tech stack they’ll need and helps them plan their work, but that’s not all:
An SRS is important because it is a single source of information and expectations, which prevents misunderstandings between project managers, developers, designers, and testers.
An SRS should have enough information for developers to complete the software described. It not only lays out the description of the software under development but also the purpose it will serve: what the software is supposed to do and how it should perform.
An SRS document typically includes these elements:
Functional requirements are the goals of the new system you are designing. They describe the system and how it will function to help with a user’s tasks. They define how the system will respond to user input and have details on calculations, data input, and business processes. You can consider functional requirements a detailed description of the application’s features and the user’s needs. Without meeting the functional requirements, the system will not work.
While functional requirements specify what a system does, non-functional requirements describe how the system will do it. Non-functional requirements do not affect the application’s functionality. Even without meeting non-functional requirements, the system will perform the desired tasks.
Non-functional requirements are also important because they define the general characteristics that affect user experience. Instead of focusing on user requirements, they focus on user expectations and cover such topics as performance, security, reliability, availability, and usability.
It is best to organize the process you use to write an SRS document by starting with a skeleton and general information on the software you’re developing, and finishing by adding details to flesh out your draft. Here are six steps involved in creating an SRS document:
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The first step in the process is to create an outline for your SRS. You can create this yourself or use an existing SRS template as a starting point. Here is a basic example of an SRS outline:
Once you have an outline, you must flesh it out. Start with defining the purpose of the product in the introduction of your SRS. Here you will describe the intended audience and how they will use the product. Here’s how you should structure the purpose:
After defining the product’s purpose, summarize how it will work. Here you will give a general description of the software’s features and how they fit the user’s needs.
You will also describe the assumptions you are making about the product’s functionality and anything it depends on in the current tech ecosystem.
Now that you have written the general information, it is time to get more specific. Completing your overview before you work on functional and non-functional requirements gives you a reference to make sure you meet the user’s basic needs while you fill in the details.
This detailed description of the system’s requirements is the most essential component of an SRS document. Describe the functional requirements in enough detail so developers can get to work and the non-functional requirements like security specifications and performance.
Here is where you add use cases to vividly describe how a user will interact with your system. It is where your project’s objectives are detailed and will measure how the project is progressing during development.
The last step in creating the draft of your SRS document is adding any details that could help developers finish the job in the form of appendixes, glossaries of terms, and references.
Once you have added enough details to the SRS to describe what the system is supposed to do, it is time to have the stakeholders approve the document.
You will most likely have to make a presentation to the people involved in the development process. They may ask for changes, and you will have to update the SRS document based on stakeholder feedback before final approval.
This is a good sign. It means both developers and stakeholders are making the document more precise, so the project is less like to go off track.
A use case describes how a user will interact with the system. It will describe the product from the end user’s point of view in a simple story format. Writing out use cases forces you to think through what users will do with the software and how it will respond. It is the real-life visualization of the functional requirements.
Here are steps you can follow to write a use case:
There are specific characteristics that every SRS should have. By reviewing this list and comparing it to your SRS, you can ensure that it will be a useful document for all stakeholders.
An SRS document should be easy to understand. Nothing should be vague, so there are no misunderstandings between stakeholders.
The requirements in your SRS document need to be measurable, so the finished product can be validated and verified against the specifications.
An SRS document should have enough information for your development team to finish the product and for testers to validate that the product meets the user’s need without bugs.
The requirements should fit the reality of the current environment, including the budget, timeline, and technology. They shouldn’t depend on upcoming technological breakthroughs.
Because things could change in the working environment, your SRS document should be flexible enough to allow for updates. Don’t add redundant information to multiple sections that have to be updated with each change.
Everyone on the development team should have access to the document so they can reference it as frequently as necessary. Requirements need to be precise so that team members do not have to ask for more details. They should all be available in the SRS document.
The requirements should fit each other. One section of your requirements document should not conflict with another. The document should be formatted consistently and used the same terminology throughout.
An SRS document should be detailed enough to finish the job, but should not be overly specific, because that might restrict development. A lot of development depends on third-party services that developers have no control over.
Goals in a requirements document should be precise to avoid confusion. Avoid the following:
Here is a trimmed down example of an SRS document for an enterprise chat app called eChat:
This document details the project plan for the development of “eChat.”
It is intended for developers, designers, and testers working on “eChat” as well as project investors. This plan will include a summary of:
Companies need remote communication tools, especially now that more people are working from home. The problem is that most companies end up using multiple applications to accomplish this: one for text chat, one for video chat, and one for conferences and meetings. “eChat” will solve this problem by combining these features in one application.
The customers will be enterprise companies. It will not target the general public.
These applications will connect to a REST API built with .NET Core to store and retrieve data from a MySQL database.
Authentication will be through existing LDAP installations.
The developers on the “eChat” team will be responsible for writing all the code for the application, developing the database, and managing releases.
There will be a class of users called admin that will have permissions to access all functionality of the app, including:
Standard users will have access to all functionality of the app except those listed above.
An SRS document is a necessary part of completing a software development project. It is the roadmap that gives direction to everyone involved in the project, so the final product meets the user’s needs.
Without a complete SRS document in place before you start a project, it will be hard to tell when a project is finished and could sidetrack development into creating unintended features. An SRS document gives you the ability to estimate a project accurately and assign tasks efficiently.
Creating an SRS document can be a time-consuming, meticulous process. Fortunately, the team at Relevant has helped over 200 companies create SRS documents and launch new products. We are ready to help with your next software project, just drop us a line.