How do I write a Software Requirements Specification (SRS) Document?

Software Requirement Specification (SRS) is nothing but detailed documentation that outlines the functional and non-functional requirements of the software application that is to be developed. The SRS document is created on the basis of the agreement between the contractors and the customers. It also includes use cases for software system interactions.

SRS must be in line with other essential documents such as system requirements specifications and software design documents. Read this blog to know more about the SRS document.

1. What is a Software Requirements Specification (SRS) Document?

A Software Requirements Specification document is an integral part of the bespoke software development process as it gives a complete overview of the software project. If the SRS is perfectly defined, then communication between the modules, hardware, and human user interactions will go great. The writing of SRS documents is carried out with the involvement of business analysts, lead developers, and project managers. Before launching a new software product, writing an SRS is a very crucial step.

The Software Requirement Specification holds a huge amount of information like –

  • Functional & Non-Functional Requirements
  • Product Functionality
  • Tech-Stack to be Used
  • Development Process
  • Delivery Estimates
  • Risks Handling
  • Use Cases
  • Assumptions, Constraints, & Dependencies

2. Why is SRS Document Important in Custom Software Development?

Creating a system requirement specification for software is one of the most important things to start with. It characterizes the general description, objective, and scope of the software. The SRS is a document that clarifies the owner’s requirements, market requirements for the product, and development requirements. If the specifications are clear and complete, it can prevent spending more time correcting the errors and reimplementing the software features. Through SRS, the project development team can build the software and ensure that it has all the essential features that users want. It is a document specifying all the necessary and basic features to make the app work.

3. How to write an SRS Document

If you have an intuition of SRS document and product description being the same then probably this is one of the greatest misconceptions. Both things are different. The product description showcases details of the project and describes how it functions. But on the other hand, the SRS description is more about how each functionality or feature in the entire application is developed and how it works. There is a standardized way of writing SRS documents, let us see each of them step by step method

3.1 Define the Purpose With an Outline

In order to start with an SRS document, the first step is to outline the purpose and establish an overview of what has to be included. 

An SRS document is an overview that typically includes the following sections: 

To start with it has an introduction, then you can add purpose, intended audience, intended use, project scope, definitions, and then an overall description of the software. You can also define user needs, and understand dependencies and system features and requirements. This consists of functional requirements, external software interface requirements, system features, and non-functional requirements.

Now when you are crafting a purpose, you must keep in mind to involve all the stakeholders, and users and design functionalities according to that. If you want to design a good purpose then make sure to include these two aspects in mind

  • You must know the scope of the application, after knowing what value will the scope deliver.
  • You must also know the target audience and also showcase relevant reasons why and how developing this app will make users’ lives easier.

To simplify, these are the points to be included in. 

In this Introduction section, we can take the following subparts

  • Purpose
  • Intended Users
  • Scope
  • Definitions and technical terminologies

3.2 Detail Your Specific Requirements

When you draft your project specifications, you must plan in order that your development team meets the criteria, we need to offer as many details as possible. This can be intimidating at first, but it becomes less so as you categorize your requirements. The requirements are divided into some of the following common categories:

Functional Needs

Functional requirements are critical to your product because, as the name implies, they give some kind of functionality. You may also have requirements outlining how your software will interact with other tools, which leads us to external interface needs.

Non-functional Needs

Nonfunctional needs are also equally considerable as functional requirements. Some of the major examples of non-functional aspects are the performance, quality, safety, and security of developed apps.

We can also say that depending on your industry, the importance and demand may vary. There are dynamic changes made in the different industries and sectors which demand the tracking and accounting of safety.

External Requirements 

External interface requirements are a subset of functional requirements. When working with embedded systems, these are very critical. They describe how your product will interact with other parts.

System Specifications

System features are an example of a functional need. These are the features that a system must have in order to work. This includes requirements surrounding users, their devices, operating systems, hardware, software, and several other functions too.

3.3 Communication With A Stakeholder

There is a first layer often used to communicate with stakeholders. That layer should be transparent and uncomplicated. Here we want to know how this layer will help us to meet the needs of stakeholders regarding their product expectations. When you converse with the stakeholders and ask relevant questions you will get a hazy picture of their needs. However, this is an excellent start to conveniently move ahead and find what consumers actually want.

You initially start talking to the clients to showcase your idea during the Pre-Sale and Kick-Off call and see whether it is a good fit or not. To grasp the client’s notion, we try to crystallize even the smallest aspects of him or her.

However, simple communication does not provide enough information about the product’s target audience as well as their wants and needs. You also need to regularly update clients and then continue with the discovery step in order to make it apparent.

3.4 Define your Product’s Purpose

In the above purpose section, we have tried and discussed how SRS establishes the firm’s expectations that we will meet throughout the SRS. When identifying this objective, keep the following points in mind: 

Intended Audience and Purpose

You need to define who will have access to the SRS and how they will use it in your organization. Developers, testers, and project managers may be included. Stakeholders from other areas including leadership teams, sales, and marketing could also be included. Defining this now will result in less work later.

Product Description

What are the intended benefits, objectives, and goals for this product? This should be related to overall business goals, particularly if teams other than development will have access to the SRS.

Definitions and Abbreviations

It is critical to define all the technical terminologies and terms for users to sound relevant. You can simplify the terms and put them into the form of a glossary for users to understand what it means and where to use them. 

3.5 Getting the Approval

The moment you get done drafting your SRS document, it is now time to check whether you have included all of the relevant elements or not. You’ll need to present it to your stakeholders and get it approved. You’ll almost have to present to all stakeholders engaged in the development, software design, and testing stages. If you haven’t articulated enough, delegate this task to the most capable members of your team.

Be prepared for them because there can be many modifications or adjustments when they review it. You might have to amend the documents to see what changes it reflects. It will be careless not to include any updates, and the final product may suffer as a result.

4. Key Components of an SRS Document

4.1 Functionality

One of the most critical components of the SRS document of any project is the description of the functional requirements of the system, which are provided to the software development team by the customer. The functional requirement is considered the goal of the new system. In the functionality section, all the features and alternative organization methods are well-organized. Besides this, the custom application development tools like modeling tools and requirement tools are employed to hold the functionality. Some common types of functional requirements are: 

  • Reporting Requirements
  • Legal Requirements
  • Authorization Levels
  • Business Rules
  • Transaction Handling

4.2 Reliability

Reliability is a component that ensures that the software system consistently works well and performs all the functions without failure. Reliability addresses the user’s concern about the failure of the system. Therefore, while specifying the system’s reliability requirements, the development team should follow suggestions:

  • Availability 
  • Mean Time To Repair (MTTR) 
  • Mean Time Between Failures (MTBF).

4.3 Usability

The usability section in the SRS document is the ease with which the users can learn and operate the system by preparing inputs & interpreting the outputs. The usability specifies the required time for training the different types of system users and time for the measurable tasks for particular tasks. This requirement must support the following perspectives for its users:

  • Intuitiveness
  • Efficiency of use
  • Low Anticipated Work-load 

4.4 Performance Requirements

The performance requirements are one of the components that specify how the system works and outline its response time. Assumptions and dependencies might affect the performance of the system. Besides this, it notifies the response time of the transactions, throughput & capacity of the system, the resource utilization information, and the details about future upgrades. Also, the performance requirement must make it clear to the users, what will be the system’s action-response time. If it is low then how can the client improve it to make the workflow smooth?

4.5 Security

Security is an essential aspect of the custom software development process. The SRS defines the system’s security aspects and the user’s concern for how the software system is a security component also ensures that the system is safe against all intrusive faults. It should also answer a user’s query about the system login mechanism being secured.

4.6 Limitations & Constraints

The details about the limitations of any other constraints that may affect the software to some extent are specified in the software requirement specification document. Any sort of hardware limitations is also included here as the users must have a clear idea of how the software will work and what hardware support it will need. 

4.7 Software Interface

The software interface section in the SRS document defines how well the software can communicate with other applications and does it couple well or not. This aspect is necessary as there might be a need for the software to work with another system to fulfill the client’s requirements. This section satisfies the user’s concern about how easy it will be to interface the system with another application. It is important, we must know about the external interface requirements of your software product.

Each interface in the software defines:

  • Details of the interface
  • Purpose of interfacing software

4.8 Hardware Interface

The hardware interface enables the users to know how portable the software system is and will be easy to transfer from the current hardware system to another to use the system. A few common aspects like the portability of the data, programs, developer documentation, and end-user affect the most when eliciting the hardware interface requirements. Besides this, the hardware interface must define the cost of the process.

4.9 Licensing Requirements

This section defines the licensing requirements and the cost of the software system. It answers the user’s query about the system licensing details like its duration and cost. The licensing requirements specify the possible ways that the users can purchase the software. For instance, automated or manual delivery of the license. Besides this, it also describes the types of licenses and restrictions to be applied to the software. 

5. Methods to Collect Information for SRS

Information gathering is one of the most important factors in the software requirement specification process to ensure the project’s success. There are different methods to ensure the development team receives the optimal requirements. Here are some of these methods: 

5.1 Questionnaires

With questionnaires or surveys, the data analysts can collect information from a large number of audiences in a relatively shorter period. This method is helpful when you have stakeholders in different geographical locations. The questionnaires focus on asking questions about the project objectives and end users’ requirements. The questions can be like – What features do you need in the system? Who will deliver the input and the output details for the features? What will be the outcome of the system? What next is in line?

5.2 One-on-One Interviews

One-on-one interviews can help in identifying the prime functionalities that users will want in the system. The purpose of the interview is to ask open-ended questions that help obtain valuable information from various individuals about the current system and their expectations of the new system. 

5.3 Group Interviews

Conducting group interviews of people from the same position helps in gathering the information much faster than one-on-one interviews. With group interviews, more thoughts can be generated, and a clear perspective can be identified from the entire team who is going to use the system.

5.4 Analysis of Current Documentation

Analyzing the system’s current documentation is a useful technique for collecting SRS information as it gives a clear idea of the working pattern of the business that is going to use the new software system. It also presents the details about the stakeholders involved in the system. This can help the analysts to prepare interview questions or surveys for the stakeholders and get additional requirements. 

5.5 User Observation

Interviews and questionnaires provide user feedback based on the questions asked by the software development team, but direct user observation can give precise and well-suited requirements that the team is looking for. To get a better understanding of the working style of the business or the current system they are using, the analyst can observe the user. This method enables validating the previously collected data and collecting the correct requirements for creating a system.

5.6 JAD & AJAD

Joint Application Development (JAD) is a contemporary method of collecting information introduced to solve users’ problems. It reduces 40% of the time as the users, and the key members of the system are involved in the process. The aim of this method is first to get the right design and then reduce different iterations.

Automated Joint Application Development (AJAD) is a newer method to collect SRS information. The goal is to encourage team interaction and keep technology as the centerpiece. Using AJAD, the analyst can identify business activities and data to display results. 

6. Benefits of Writing an effective SRS

The good practice of the software requirement specifications enables the software developers to create a user-centric system and achieve the following advantages for developing custom software: 

  • SRS specifies the problem of the application that requires it to be changed according to the customers’ demand.
  • It offers validations to the hierarchy of requirements and strategies of the development team.
  • The SRS is a complete and accurate document of logical statements.
  • It showcases the needs and preferences of the end-users.
  • Its functional requirements give the best implementational approach to the software developers.
  • SRS holds the technical requirements that show what the system is required to do.

7. Conclusion

A software requirement specification document is a must when the software development company is creating a new project. It is useful for both the customers and the development team, as it results in the system’s outcome. The above-listed points can help follow good practice of the SRS, which can eventually benefit the successful development of the project as per the user’s requirements. 

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Itesh Sharma

Itesh Sharma is core member of Sales Department at TatvaSoft. He has got more than 6 years of experience in handling the task related to Customer Management and Project Management. Apart from his profession he also has keen interest in sharing the insight on different methodologies of software development.

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    1. Stephen

      As we know Software development is a complex process. It contains multiple processes within itself. Hence proper documentation of all these processes is very necessary. For covering a detailed description of the technical specifications and requirements of an app or software SRS document is very necessary. Once you have all specifications in an SRS, you can easily manage them throughout your development process.

    2. Sophia Rodigruez

      Writing an SRS document is a very essential process while you are considering software development. This article is very helpful for anyone who wants to write an SRS document. This article will help you create a comprehensive SRS that covers business characteristics, technical details, and user data will pay off with a stunning product that meets your expectations.