What Is Software Requirements Document & How to Write It
After having a brilliant business idea, the last thing you want to do is write lengthy technical documentation. However, software requirements document (SRD) also known as software requirements specification (SRS) is essential for the successful development process.
We aimed to make the article complete and accurate. That's why it takes into account both the customer's and the developer's points of view.
How to create a perfect SRD? We will answer this question and share:
- critical information about SRD
- helpful requirement elicitation techniques
- steps of creating SRD + ready-to-use template
- ways of writing use cases with examples
What is Software Requirements Specification document?
The software requirements document (also known as software requirements specification) means both software requirements documentation and system requirements doc. Sometimes, the SyRS abbreviation stands for the latter, but most professionals use them as synonyms. SRD as a software requirements doc is more extensive, as it holds information about user requirements and other details aside from system needs.
This document outlines what you need and expect your product to do. The more detailed SRD you create, the fewer delays you will face seeking professionals. With a single glance at the software requirements doc, any stakeholder understands what the finished product should be.
A requirements specification is necessary if you plan to create your own startup or build a software product. A good software requirements document is a reference point for everyone involved in the project. SRD is vital for software developers, designers, testers, operations and maintenance staff, and even investors.
We've already covered some key aspects in the previous article. It includes a downloadable software requirements template. You can use it to identify the quantifiable parameters and set the constraints of your project.
Why a Software Requirements Document is Important?
Startups are often chasing impossible deadlines. They don't have time to waste on preparation. Product owners believe it's possible to produce quality software without creating a system requirements specification. Before you follow in their steps, look at the benefits of a good SRD:Startups are often chasing impossible deadlines. They don't have time to waste on preparation. Product owners believe it's possible to produce quality software without creating a system requirements specification. Before you follow in their steps, look at the benefits of a good SRD:
How to use problem pyramid to write SRS?
The software requirements document spans 5 to 10 sections. They include business context and purposes, functional and non-functional requirements, additional information. In a nutshell, SRS holds answers to the following questions:The software requirements document spans 5 to 10 sections. They include business context and purposes, functional and non-functional requirements, additional information. In a nutshell, SRS holds answers to the following questions:
If you have trouble answering, use the problem pyramid to help you along. It's a business analytics method that simplifies requirements elicitation.
Writing a system requirements specification seems like a tedious task. You can make it easier on yourself by using the problem pyramid and following these steps:
How to create requirements document: guidelines
The most important source of information on writing an SRS is an ISO/IEC/IEEE 29148. This standard was adopted in 2011 and superseded an older IEEE 830-1998. The following plan of writing SRS is based on the latest standard.The most important source of information on writing an SRS is an ISO/IEC/IEEE 29148. This standard was adopted in 2011 and superseded an older IEEE 830-1998. The following plan of writing SRS is based on the latest standard.
1. Introduction
Setting the goal is half the battle. First of all, you need to identify the purpose of your product. This short section summarizes the whole document, highlights the concept of the project. It's an integral part of the project specification that answers the first question of the development team: "What will we work on?".
When you create an app, get a clear picture of the industry you wish to conquer and the competition. Depending on whether you offer retail products, consulting services, or SaaS solutions, the requirements will differ. You create the file for the current and future specialists working on your project.
They need to understand your business context. Who is interested in the development of this application? What purpose does it serve? How is it different from competitors' offers? Defined business context showcases key priorities and helps organize the development process.
The introduction usually includes the project's scope. This paragraph describes the specifications of your product: its advantages, unique features, objectives, and more. It's crucial for the precise timeline and budget estimates and the fruitful collaboration with the services provider.
You should also mention the target audience of the application. Who is the intended user? What are their preferences, wishes, and fears? The users can be divided into several groups according to their access rights to ensure the system's security and reduce risks. You can also mention the users' locations and devices.
The section on acronyms and definitions isn't obligatory, but it's a great idea to include it in your high-level requirements document. It prevents misunderstandings, especially if your market niche is highly specialized. Do not expect IT experts to possess in-depth knowledge of medical terms or scientific nuances; instead, create a helpful glossary.
Finally, the introduction can include references to your business, similar projects, as well as your expectations and hopes.
2. General system description
The cardinal rule of writing is to go from general facts to specifics. That's why you should give an overview of the product you build before listing specifications.
To begin with, write whether it's a new application or a system that already exists. Then, you can describe the project's context, including its primary interfaces and structural elements: Illustrations, diagrams, tables will be beneficial for the readers.
Next, note the modes and states of the future system, as well as its main conditions, capabilities, and constraints. At this point, it is enough to mention these aspects; you will give a detailed description of them in the next section.
The general system description must contain assumptions and dependencies. List the factors that can affect the relevance of this SRS version. What internal and external occasions may change your requirements and the project's scope? Write them down to minimize risks. For instance, you might need software components you're reusing from another product, making it one of your project's dependencies.
Operational scenarios round up this section. They describe how different parts of the system interact with each other, the user, and the environment. Think of them as sequences of events that happen to the user.
3. System capabilities, conditions and constraints
The detailed description of requirements is one of the essential components of software requirements documents. It helps the development team to make your plan happen and ensures you receive the product that fits your needs.
This section helps programmers, designers, and other IT specialists to understand your demands. Some of them are standard for all software products, such as:
- database for storing product or user information;
- frontend for comfortable user experience and backend for data processing;
- user hierarchy with separate access rights and features for admins;
- third-party software products integration;
- cross-platform support for desktop, tablet, and mobile users;
- scalability to accommodate the project's future expansion.
These are non-functional requirements that can be the same across many industries. They elaborate on the performance of the system, showcase HOW it should operate.
Functional requirements outline the system's behavior or WHAT it should do under different circumstances and in various use scenarios. They make people fall in love with your products, and non-functional requirements make them stay.
Let's look at the example of an appropriate representation of each function.
Now let's consider different functional requirements examples. There are four common physical requirements:
- construction (desired device compatibility)
- durability (staying power of the system)
- adaptability (growth, expansion, capability, contraction)
- environmental conditions (external factors influencing the app)
Logical data requirements include data types, its organization structure, connections, and more. You can either create a visual model to represent the requirements or spell them out in writing.
Other requirements deal with:
- App users
- Information management
- Performance and quality
- Policy and regulation
- System's lifecycle
4. System interfaces
In this section, you should explain the dependencies among system components. These may include existing elements, those under development, and future components. It's necessary to think about both human users of your system and other applications that will be connected with it.
You can set requirements for 4 main types of interfaces:
- User
- Hardware
- Software
- Communications
5. Requirements traceability matrix
RTM is a useful tool that ensures every requirement is covered by testing. It's an essential part of an SRS that enables smooth development and helps achieve your goals. RTM is a table that holds a list of requirements and change requests.
6. References
Add references if you aim to write an excellent SRS. The perfect way to organize them is a table. Include links to every file, its creation date, author, and comments.
7. Glossary
The list of terms and acronyms can be present in the introduction to the software requirements documentation. But if they are numerous, it's better to create a glossary.
8. Revision history
The long-term projects may have several versions of the specification document. It's convenient to organize them in a table with columns named: "Version #", "Date", "Name", and "Description".
9. Appendices
This section is not mandatory, but if you have not included individual pieces of relevant information in other parts of the software requirements specification, add them in the appendices.
Difficulties for creating software requirements document: common mistakes
Problem #1 You don't know how to write high-level requirements
Use the method described in the first part of this post. Start with a brainstorming session and a big-picture mind map for creating an actionable SRS doc. It is much easier than developing the document from the ground up without previous experience. Take real-life users into account to break down the problem.
Problem #2 You struggle with structure and formatting
The easiest way to achieve clarity is to use a reliable software requirements document example. If you have some parts of software requirements specification templates and no idea how to handle them, reach out to our team.
We'll help you develop a comprehensive SRD for your project. You can also send your project requirements document to Freshcode to get a quote.
Problem #3 Your document is overcomplicated
Standardization of the language of your system requirements document isn't a challenging task.
Follow several simple rules for best results:
- Avoid jargon and words with multiple meanings that might lead to interpretation difficulties. Define terms before using them.
- Use references, such as "as shown in" or "in accordance with," for tables, images, or charts.
- Minimize passive voice and ambiguous words, such as efficient, fast, easy, normal.
- Use the word "shall" for absolute requirements and "may" or "should" for optional ones.
Problem #4 You are afraid of including too many details
You should explain everything, no matter how obvious it might seem to you. Make your software requirement documentation as detailed as possible. Imagine the reader has zero knowledge about your project and niche.
Do not expect the local service provider to read your mind and write everything down to ensure efficient collaboration. You create a software requirements specification document to help the developers, not to confuse them, so be generous with information without going on tangents.
The more precise your demands are, the better software developers will understand your needs. Here is a subtle trick to make most of your SRS. Avoid these terms at all cost:
Superlatives
Wrong: The system shall be the best among similar products.
Right: The system shall implement feature_1, feature_2, and feature_3.
Subjective terms
Wrong: The software interface shall be user-friendly.
Right: The software shall be installed in under 1 minute.
Ambiguous phrases
Wrong: The project shall be completed in a minimum possible amount of time.
Right: The project shall be completed within 2 months.
Comparative phrases
Wrong: The application design shall be better than that of the main competitors.
Right: The application design shall contain three primary colors.
Loopholes
Wrong: The system shall employ material design, if possible.
Right: The system shall employ material design.
Hopefully, this brief guide and software requirement document template will come in handy and help you to speed up the development of your project.
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