Software requirements specifications

Guide to Software Requirements Specification (SRS) Document 2021

Trying to create a software product without the Software Requirements Specification document is like sailing the ocean without a map.

Why Is SRS Important?

A software requirements specification (SRS) is a document that explains in great detail the functionalities of a software. It clearly states and provides the overall description of the features the software must possess and the product functions that must be satisfied. 

The SRS is essential, especially when you want to create a software product or you wish a product to be developed for you. The SRS document removes all the ambiguity associated with non-written forms of project presentation, such as oral discussions. An SRS makes product development easy and prevents incorrect interpretation, which leads to the creation of a wrong product and, ultimately, the project failure. An SRS ensures that everything required is in written form. It also includes the development process. 

Let’s say, you want a business app to be developed for you. The next step will be to find developers with suitable engineering requirements who will be able to create the app that has the desired specifications. Without an SRS document, developers are more likely to assume and implement something they think the app should be instead of realizing your exact idea. It, in turn, can cost the client time and money as the app will have to be modified over and over again. However, an SRS document ensures that all the app specifications are noted down on paper. It will provide methodologies to follow to ensure quality assurance of the product. 

The SRS enables the development team to:

  • Come up with an agile workflow plan and timeframe for the app development.
  • Estimate the overall cost for the app development.
  • Determine the programming stack required for the implementation of the required app specifications.
  • Formulate a test plan and perform software testing of the product in line with the stated desired business outcomes.

Other uses of an SRS are:

  • It outlines the lifecycle of the product and the associated dependencies the product has.
  • It helps the final user to understand how to use the product.
  • It provides a clear overview of the whole project so that investors can understand the app features and how it relates to business requirements. It will help them make investment decisions in your favor.

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What Does an SRS Document Consist of?

An SRS document must contain all the necessary information, which ensures complete product creation. Additionally, it also consists of a description of how the software must operate. 

A typical SRS document must consist of:

  • The purpose that the developed product must accomplish.
  • The functionality of the complete product. All separate functions of the product are listed and how they interconnect to provide a seamless experience.
  • The expected performance of the product with actual figures. For example, a website development requires performance parameters, such as page load time and the number of simultaneous visits that can be handled.
  • The compatibility of the software with other software and the underlying hardware interface. It helps to assess the product’s flexibility and its interaction with other external interface requirements and programs. 
  • The test cases that the product testers will use to thoroughly evaluate the product’s operation.
  • The product’s interface. The user interfaces are essential for creating a pleasant user experience and easier navigation and performing of tasks.
  • The environment the software will operate in. By stating the product’s operational environment, it becomes easier to identify the limitations and design constraints of the product. It also describes the product’s maintainability once it’s complete.

Functional vs. Technical Requirements of SRS

Functional Requirements

These are product features that enable the end-user to accomplish a specific task. It describes all the components of the operating system and how they will achieve the required expectation. Functional requirements define how the system will operate upon the selection of certain user inputs. It includes how the data is inputted and the processes necessary for the data computation. The functional requirements are essential for the software operation.

Technical Requirements

The technical requirements are focused on the non-functional features of the product. Even without the technical features, the product will continue to operate. But they are necessary as they entail details that affect the user experience. The technical requirements contain the expectations of the users and fulfill their user needs.

The expectations include:

Usability

Product usability refers to the user experience (UX) and the user interface (UI). The UI is associated with the ease of the product’s use. It also includes the layout of the product components. The UX, on the other hand, is responsible for how the user will feel upon interaction with the product. 

Availability

For software products such as a website, availability refers to how often the site is online.

Security

It defines how secure the product must be against various threats that exist. A more secure product instills confidence in users.

Performance 

The performance is stated with actual figures that the product must satisfy to be within the expected range. The SRS also notes down the minimum limits that the product must have without any deterioration in performance.

How to Start Writing an SRS Document

An organization can start from scratch, permitted that it has the time and resources to do so. Creating an SRS from scratch takes much time and is prone to lots of errors, especially if the staff is not familiar with creating an SRS document. However, an alternative is to find a template and edit it. A template will provide the general outline of the requirements required in an SRS document. The organization can then personalize the content to suit their specific requirements. One of the best places to get a standard SRS template is from IEEE (Institute for Electrical and Electronics Engineers). IEEE is an electronics and informatics organization that develops and defines the standards used in the industry. 

Writing an SRS Document Template

For those who need to create the SRS document from scratch, below are the stages that will enable them to come up with a comprehensive SRS document.

    1. Come Up with an Outline

      The outline of the SRS document will provide the document’s skeleton, which you will use to add additional detailed information. To ensure that you don’t miss any stages, it’s best to construct the outline from a template.

    2. Purpose of the Product

      The next stage is to define the product’s purpose. The purpose states whom the product is being made for, its helpfulness, and the value it will bring to the intended users. Also, this stage clearly states how the end-users will use the final product. It also entails how the target audience will interact with the product.

    3. Summary of Operation

      In the product operation summary, the system features of the product are described. Also, this stage provides the product’s functionality.

    4. Functional and Technical Requirements

      This stage is crucial. It provides the detailed operational procedures of the expected final product. It specifies the exact requirements for developers to create the product. The technical requirements will be used on the end stages of product development to make the product more presentable, safe, and providing a pleasant user experience. The project objectives are stated at this stage. They also provide the guidelines to determine the progress of software development. Included in this stage are cases that describe how the user will apply the end product.

    5. Navigation

      The next stage, which is also the last, is about providing means for easy navigation of the document. It could be in the form of table contents, glossary, and appendixes. It makes it easier for anyone to identify and locate any particular section.

    6. Feedback

      Once the SRS document is complete, it is presented to the stakeholders, project managers, and the development team. Changes are common during this stage as some of the SRS content might require modifications from either the development team or stakeholders. 

How to Check if Your SRS Is Good?

For a project to be completed successfully, a good SRS must be available to provide all the necessary and relevant information. After SRS completion, you must crosscheck if it satisfies all the requirements of a quality SRS document.

Correctness

A correct SRS covers all the specifications expected of the software operation. Usually, the correctness of the SRS document is modified and adjusted according to user review. The user reviews make it easy to correct some of the factors that may have been overlooked during the initial drafting.

Consistency

A good SRS document must be in agreement throughout. Conflicting statements might halt the development of the product with the need to resolve the conflicting sections. Moreover, the document must contain the same terminology to prevent confusion associated with inconsistent content.

Accuracy

The SRS document must be precise. If there is a need for specific values, state them. Ambiguous words with no clear meaning must be avoided. For example, the app must be “good”. What is good? It is a subjective term prone to different views and interpretations. As such, the need to be concise is of utmost importance when creating an SRS document.

Flexible

The SRS document must be flexible to allow any future adjustments to be implemented in later stages. For example, new security is introduced after the security section of the product has been completed. The SRS document must allow for discoveries to be applied even after initial development.

SRS Examples

Below are some of the examples of the SRS for different industries.

SRS for hospital management system

SRS for restaurant management system

SRS for online reservation system

SRS for a banking system

SRS for inventory management system

SRS for mobile app

What Is the Difference Between System Requirements Specification, Software Requirements Specification, and Functional Requirements Specification?

System Requirements Specifications

System requirements specifications refer to the physical components of a machine. For example, in a car, the system requirements would cover components: the brake system, lights, security system.

Software Requirements Specification

The software requirements specification refers to the software that is required for the proper functioning of the product software system. It describes the functional and non-functional software requirements.

Functional Requirements

It refers to the specific requirements for the product to operate. Mainly, it includes what the software needs to accomplish, for example, the measurement of fuel in a car.

Is It Safe to Share SRS with Contractor Developers Before the Hiring Contract Is Signed?

Yes. Experienced CTOs are usually not afraid to share the specification because they understand that the idea described on paper is not the same as its implementation and development process. Therefore, hardly anyone will be able to repeat and implement your software project faster and better than you.

At the same time, openness at this stage allows the potential contractor to better assess the task, to understand whether they have the resources and expertise to perform the required work. Openness leads to smarter and more thoughtful decisions, which can ultimately save you a lot of time and money.

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FAQ

What is SRS?

A software requirements specifications (SRS) is a document that describes how the software is to be developed. It provides in great detail the functional and non-functional requirements of software production. Moreover, it includes the cases that define the user experience expected of the final product.

Why is the SRS document important?

The SRS is an essential document that lays out the framework. It will guide the software engineering team during product development. It is essential for easier production by minimizing the time and costs of software development. 

What SRS is needed for?

It aims to provide critical software information to the developers and ensure the development of the expected product. The software requirements document acts as a reference document to make sure that after completion of any stage, all the requirements have been fulfilled.

What are the contents of the SRS?

The SRS document contains all the information about the project. It includes how the product must be developed, the properties it must possess, and how it must function when it’s completed. It also consists of the functionality and the expected performance of the product. 

What are the main characteristics of useful SRS?

The end product is as good as the quality of the SRS document and the expertise of the developing team members. As such, a quality SRS is required. An SRS document must be correct and consistent to prevent confusion. It should not be ambiguous to avoid a different interpretation of the desired outcomes. Finally, the SRS document must be flexible to allow future adjustments in case the need arises.
Written by
Svetlana Shevchuk

Digital Marketing Specialist at YouTeam, a Y Combinator-backed marketplace for building remote dev teams.

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