Software Requirements Specification, or SRS document, is definitely one of the most critical documents in software development. When you decide to create a website, an app, or any other software, it serves as a roadmap for an entire project.
No wonder why SRS is often seen as a cornerstone of proper development and long-term success. After all, it provides a solid foundation for working processes and sets communication on the right track.
So, what is an SRS document, and how is it created? In this article I will share all the needed explanations and writing advice. Moreover, I will provide you with a good SRS document example that you can use as a reference.
What Is a Software Requirements Specification (SRS) Document?
The first thing to clarify is quite an obvious question: what is an SRS?
A software requirements specification is a document that provides a detailed overview of your software product, purpose, requirements and features.
A typical SRS document includes:
- The purpose of your product – including its audience, use cases and product scope.
- An overview of your product – including your users’ needs and the assumptions surrounding your product.
- A detailed rundown of your specific requirements – including functional requirements, interface requirements, system features and non-functional requirements.
Who should write an SRS document? It is generally created on the side of the team that will be in charge of the whole development process. It could be a product or project manager. A rare yet possible option is when it is written by a business analyst, technical engineer, or any other specialist who is familiar with the future product.
Who are readers of the SRS? First off, developers. They need an SRS to understand the idea of the product and all the technical details behind it. Other than that, the document comes in handy for marketing specialists, stakeholders, co-founders, UI/UX designers, and more. Finally, it allows everyone to quickly become familiar with the project and have a helicopter view of possible results.
What does an SRS document contain?
A Software Requirements Specification document contains a significant number of details. To make your writing simpler, I suggest dividing a document into several logical sections:
- Introduction
- Purpose
- Overall description
- Intended audience
- User needs
- Intended use
- Scope
- Definitions and acronyms
- Assumptions and dependencies
- System features and requirements
- Functional requirements
- Non-functional requirements
- External interface requirements
- Systems requirements
Other important things to include:
- Risks
Carefully analyze all possible scenarios when something can go wrong. Identify problem areas in advance and discuss solutions with the team. This information may be pivotal to having a clear vision of what to do in case of each of the problematic issues.
- Time and estimates
Evaluate all processes, and define the desired timeframes.
As you can see, the content of SRS is quite comprehensive. At first sight it may even overlap with similar documents like Statement of Work (SOW) or Request for Proposal (RFP). All have similar content and structure, but each serves a different purpose. That's why it is so important to know at least the main idea and understand the occasion for each of them well.
How to Write an SRS Document
As experience will show, writing software requirements specification is easier when you follow the right set of steps. Below I’ve provided the step-by-step algorithm that I find really helpful. Keep in mind that each step should have a purpose and goal, and not just be implemented.
- Communication with a stakeholder
Everything starts with proper communication. It typically happens between two sides: product owners (stakeholders) who share the vision of the product, and a development team or other specialists who will be responsible for implementation.
It is beneficial for product owners, and the development team, to hold a meeting to discuss what should be done and how. The key point here is to make sure everyone understands each other well and there is enough information to form functional and non-functional requirements.
- Research
This step is pivotal to being aligned with business needs, goals, and priorities. Conduct thorough user and technical research. Find a suitable business model, analyze existing solutions on the market, compare different project roadmaps, and more.
Usually research takes up to 4 weeks to carry out the data gathering and analysis.
As a result, you should be able to define:
- target audience (customer personas), users' problems and needs;
- how users might interact with the product;
- hypotheses of potential solutions to problems;
- use cases (description of all features). Keep in mind that for each type of end-user, there should be corresponding use cases;
- user stories (the outcomes and benefits obtained by a user while using a feature);
- timeline, and technology.
It is advisable to involve the whole team in this phase to explore a wide set of ideas, share thoughts, and offer more efficient solutions.
- Defining the functional and non-functional requirements
Functional requirements determine the system's functionality, software structure, and all elements within it. Non-functional requirements are more descriptive specifications of functional requirements. They describe how all features should work in certain conditions like in terms of performance, localization, scalability, etc.
- Draft
After completing all the steps, it is time to check whether everything is fine with the document. Prepare an initial SRS example and discuss it with stakeholders and developers. Just like with any other written document, there are high chances of overlooking or describing some fragments incorrectly.
Characteristics of a good SRS document
While reviewing a lot of SRSs, I discovered some characteristics that make a document more effective:
- Suitable for both technical and non-technical users
An SRS document is truly effective when both technical and non-technical audiences understand it. Both developer and user (the client) should be able to read it without any difficulties. For this reason it is highly important to translate all complex terms into simple language.
Advice to make the content resonate well with anyone with any background:
- don't use technical terms without an explanation;
- alphabetize and bold that list of terms;
- add an acronym section to clarify terms that you are using in this document, terms that may have ambiguous meaning.
- Clarity and simplicity of language
The content and language of the document will mainly define how well developers understand requirements. Here are the rules to make it as simple and laconic as possible:
- avoid ambiguity and subjectivity;
- don’t use vague subjective terms unless you define what these terms mean;
- don’t write in a possessive voice;
- don’t write 'I will', or 'we will’, instead, use words like 'the system will'.
- Consistency
The document should have consistent logic, terminology, and formatting style. One paragraph should not conflict with another.
- Excellent visualization
The next characteristic of good SRS is visual clarity. Don’t skip the usage of diagrams, mind maps, schemes to represent all components and their interconnections in a clearer way. For instance, draw.io is a great app for this purpose that allows facilitating SRS creation. You can use it to create context diagrams, use case diagrams, and more.
Some cases may also be useful AS-IS and To-Be process models that display relations in different timeframes:
- An AS-IS diagram represents current processes, which helps to identify problematic areas and risks in the present time;
- A To-Be diagram predicts how existing processes may revolutionize later, so avoid possible glitches in the future.
- Specific performance criteria
All specifications should have a certain measure or description of the exact criteria for performance. It will be helpful to validate and verify the product later.
- Flexibility
Leave space to modify the document. We all know that in Agile ecosystems, projects can go around and acquire new features. Because things can change with every passing iteration, SRS should be flexible enough for any update.
Bottom line
Writing a good SRS document is critical because it allows you to:
- turn a chaotic implementation process into a structured plan;
- calculate all limitations with implementation;
- mitigate the risks early on (often there is a risk to get a product from minor to no use);
- improve communication between people from various 'sides'.
That being said, should you need to create one, it’s important to make sure you follow the best practices listed above. I hope this guide will help you to create a powerful software requirements specification and get the desired result that matches your expectations. Good luck!
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