The importance of requirements gathering to the software development process can’t be overstated. Understanding what is required to be included in the software is critical for being able to deliver a product that the client will accept and like. Once you understand all the requirements for a project, you should create a system requirements specification (SRS) document, otherwise known as a software requirements specification document. This document describes the software’s functionality and expected performance.
In the sections below, we offer information to help you develop effective SRS documents. We’ll take a look at what the SRS document should contain, describe how an SRS document is prepared, and provide an SRS document example. First, we explain why SRS documents are so important.
SRS Document Benefits
The primary purpose of an SRS document is to provide a high-level guide for how the project will be implemented. It offers a single source of truth that all stakeholders can refer to. This directional document helps to keep teams on track and ensures that all requirements are included during the development process. The SRS document can also be shown to project requesters to verify that your team understands all the requirements.
What Should an SRS Document Contain?
So, what should an SRS document contain? Starting at a high level, the document should spell out the purpose of the software, including what users will be able to do with it and how that functionality will help them. Next, the document should describe the software that will meet these needs, including a comprehensive list of requirements. Other possible elements include how the software will interact with hardware and with other software.
According to a recent TechTarget article, an SRS should reflect the following characteristics.
- Correct – accurately reflect product functionality and specification
- Unambiguous – written clearly enough to avoid misinterpretation
- Complete – contain all the features requested by the client
- Consistent – use the same abbreviations and conventions throughout the document
- Ranked for importance and stability – list requirements in order of urgency
- Verifiable – reflect only statements that can be verified — that is, quantifiably measured
- Modifiable – be structured such that requirements can be altered without impacting the others
- Traceable – include information about where each requirement came from
How Is an SRS Document Prepared?
Now let’s discuss how to write an SRS document. Keeping in mind the elements described in the previous section, it’s often helpful to create an outline before writing the document itself. The outline should contain sections like an introduction, description, and list of requirements. The introduction should spell out the following elements:
- Purpose of the software. Who will use it? How will it help them? What function will it serve?
- Business case and use cases. High-level goals of the company building the software as well as specific situations in which the software will be used should populate this section
- Intended users. Here you should include a description of the typical user, including their motivations, technical skills, and preferences.
- Acronyms used in the document. Include definitions of acronyms or jargon to help readers understand the text.
- Potential project risks. What could go wrong, and what is the plan to mitigate these situations?
The description should include the following sections:
- User needs. Not to be confused with requirements, this entry should describe must-haves from the user perspective.
- Assumptions and dependencies. Things like operating systems and how specific requirements will work together should be included here.
The requirements section could be broken down into more specific levels, as follows:
- Functional requirements. This section should list requirements that are specific to the software’s functionality.
- External interface requirements. These requirements describe how the software will interface with other components, such as hardware.
- Nonfunctional requirements. Nonfunctional requirements include things like performance and security.
- Acceptance criteria. This section details the conditions that must be met for the customer to accept the product.
While these guidelines can serve as a starting point, you should include any other sections that you think are relevant and helpful. The following chart from project management software provider Asana shows a slightly different way to conceptualize the structure of the SRS document.
Next, it’s time to write the actual document. You’ll need to expand on the outline topics, and the information should come from the requirements discovery process as well as conversations with stakeholders, including clients, managers, investors, and possibly even end users. Here are some additional helpful hints:
- To save time, you might want to download an SRS template, such as the one provided by Asana, or create one of your own.
- Choose document development software that will support your process. For example, some teams like to use Google Docs because it enables multiple people to work on the document at the same time.
- Write in a way that readers will understand. Doing so requires a solid understanding of the target audience.
- Use paragraphs, bullet points, charts, and any other visual elements you think will be helpful.
- Develop a process to integrate change requests, such as alterations to the requirements.
You may be wondering who should prepare the SRS document. Ideally, it would be anyone on the team who has a clear understanding of the project requirements and is skilled at communications.
System Requirements Specification Example
Technology information publisher Krazytech has created an SRS document using a flight management project as an example. As you read it, note that the document includes many of the sections and features we have mentioned above. The initial table of contents helps readers understand what to expect as they review, and the descriptions are clear and concise. The visual components are helpful in understanding the concepts presented.
Practice Makes Perfect
Learning how to write system requirements specification documents isn’t hard, but it may require some practice. Keys to success include understanding why the document is being written, collecting the right information, and using strong communication skills to effectively convey the parameters to readers.
