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How to write a Software Requirements Specification document

January 2, 2023
Author
Joash Ojeyokan
September 2, 2022
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A Software Requirements Specification (SRS) document is a crucial deliverable in software development. It outlines the functional and non-functional requirements of a software system and serves as a blueprint for software developers, testers, and project stakeholders. Creating a well-written SRS document is essential to ensure that the final product meets the desired objectives and satisfies the needs of its intended users.

In this article, we will discuss the key elements of an SRS document and provide a step-by-step guide on how to write one.

Step 1: Define the Project Scope

The first step in creating an SRS document is to define the scope of the project. This includes identifying the objectives of the software system, the users who will be using the system, and the features and functionalities that the software system should provide.

For example, let's say that we are creating a software system for a small online retail business. The objectives of the software system could be to provide an online platform for customers to browse and purchase products, as well as for the business to manage their inventory, sales, and customer data. The users of the system would be the customers and the employees of the retail business. The features and functionalities could include a product catalog, a shopping cart, a payment system, an inventory management system, and a customer management system.

Step 2: Gather Requirements

The next step is to gather requirements from various stakeholders, including the business owner, end-users, and technical team. This step involves understanding the needs and expectations of the stakeholders and documenting them in the SRS document.

Requirements can be categorized as functional and non-functional requirements. Functional requirements describe what the software system should do, while non-functional requirements describe how the software system should perform.

For example, some functional requirements of the online retail software system could include the ability for customers to search and filter products, add products to a shopping cart, and checkout. Some non-functional requirements could include the system's performance, such as its response time, scalability, and security.

Step 3: Define Use Cases

Once the requirements have been gathered, the next step is to define use cases. Use cases describe how the software system will be used by its intended users.

Use cases can be documented using user stories, which describe the interaction between the user and the system. User stories should be written from the perspective of the user and should be specific, measurable, achievable, relevant, and time-bound.

For example, a user story for the online retail software system could be "As a customer, I want to be able to search for products by category, so that I can find products that I am interested in more easily."

Step 4: Define Functional Requirements

The next step is to define the functional requirements of the software system. Functional requirements describe what the software system should do, and should be written in a clear and concise manner.

Functional requirements can be documented using use cases or scenarios, which describe how the software system should behave in various situations. Use cases and scenarios should include the inputs, actions, and expected outputs of the system.

For example, a functional requirement for the online retail software system could be "The system should allow customers to add products to their shopping cart and checkout using a secure payment system."

Step 5: Define Non-Functional Requirements

The next step is to define the non-functional requirements of the software system. Non-functional requirements describe how the software system should perform, and should be measurable and testable.

Non-functional requirements can include performance, scalability, reliability, availability, security, and usability. For example, some non-functional requirements for the online retail software system could include "The system should be able to handle 1000 concurrent users without a decrease in performance" and "The system should be able to recover from a hardware failure within 1 hour" etc.

Step 6: Include Assumptions and Constraints

Assumptions and constraints are factors that could impact the development or functionality of the software system. Assumptions are things that are assumed to be true but may not be guaranteed, while constraints are limitations that must be considered in the development process.

Assumptions and constraints should be included in the SRS document to ensure that all stakeholders are aware of potential risks and limitations.

For example, some assumptions and constraints for the online retail software system could include "The system will be developed using the Java programming language" and "The system will be hosted on Amazon Web Services (AWS) cloud platform."

Step 7: Define Acceptance Criteria

Acceptance criteria are the conditions that must be met for the software system to be considered acceptable by the stakeholders. Acceptance criteria should be specific and measurable and should be agreed upon by all stakeholders before development begins.

For example, some acceptance criteria for the online retail software system could include "The system should be able to process 100 transactions per minute without any errors" and "The system should be able to handle 10,000 customer accounts."

Step 8: Review and Revise

Once the SRS document has been created, it should be reviewed and revised by all stakeholders. This step ensures that all requirements and expectations have been documented accurately and that everyone is on the same page.

The SRS document should be reviewed for completeness, consistency, and clarity. All stakeholders should be given the opportunity to provide feedback and suggest revisions.

Step 9: Finalize and Approve

After all feedback has been incorporated and revisions have been made, the SRS document should be finalized and approved by all stakeholders. This step ensures that everyone is in agreement on the scope, requirements, and expectations of the software system.

The SRS document should be signed off by all stakeholders, indicating their approval and acceptance of the document.

Conclusion

Writing a Software Requirements Specification document is an important step in the software development process. It ensures that all stakeholders are on the same page and that the software system meets the desired objectives and requirements.

To create an effective SRS document, it is important to define the project scope, gather requirements, define use cases, define functional and non-functional requirements, including assumptions and constraints, define acceptance criteria, review and revise, and finalize and approve.

By following these steps, you can create an SRS document that serves as a blueprint for the development of a successful software system.

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