Excellent Software Requirement Specification (SRS) Guide

A software requirement specification (also called SRS) sets a project for success from the very beginning if written correctly. At first, the preparation of SRS may seem overwhelming.

That is why we created this blog to guide you, provide explanations to each of the SRS elements and give hints on how to improve your documentation.

 

The Definition Of SRS and Its Importance

An SRS is a software development roadmap that provides designers, testers, clients and end-users with metrics, use case scenarios, and other details of the future product. Briefly saying, it collects the clients’ demands and explanations of the development team how these demands will come to life in custom software development services.

Do thorough thinking and research while preparing software requirement specifications. An SRS will serve as:

  • a contract basis between you and a client
  • a work plan that defines the scope, time and costs
  • list of desired goals and metrics that measure the success of the finished work.

Poor gathering of requirements causes nearly 60% of project failures. If you want to avoid falling into that category – prepare an SRS that works.

SRS Fundamentals

SRS Fundamentals

A standard example of requirement specification lays out all the details that form a vision of the product, its operational metrics and potential users.

 SRS elements

  • An aim of the product
  • A generic overview of the software
  • Functional requirements (operations that a system can perform)
  • Non-functional requirements (security, performance, flexibility, etc.)
  • External interfaces
  • Design constraints

Review Of The Functional and Non-Functional Requirements With Examples

It’s the way the software requirements are called that gives a hint of their specifications. You may have guessed – functional requirements are prerequisites for the performance of the software. On the other hand, non-functional requirements play the role of additional features that can leverage the user experience. To sum up, functional requirements are a necessity, and non-functional requirements are addition and a marketing tool to some extent.

Functional requirements

They describe system responses to various inputs. Some simple examples include signing in, email list subscribing, adding items to the shopping cart, etc.

Non-functional requirements

In contrast, these requirements are extra – software still works without them. So, they impact users’ experience, not their needs. For example, “when signing in, the new user receives a confirmation email” is a functional requirement, and “the confirmation email has to be received within 5 minutes” is a non-functional one. So, the 5-minute limit probably increases user’s satisfaction, but isn’t critical for software performance.

Non-functional requirements can refer to:

  • availability
  • usability
  • performance
  • security
  • reliability

 How to document and manage the SRS

Almost every project needs proper management, and SRS preparation is one of them. Treat the document as a design process and use some tips below to organize it.

Reach For Clarity

Misty requirements may lead to chaos and misunderstanding. While preparing the software requirements specification, be clear and avoid ambiguity. Don’t use vague phrases such as “fast response” or “good performance”. They don’t communicate any essential information. Instead, provide measurable goals, such as a “5-second response”.

Flexibility Is Key

Change the document if needed. Constantly reach for business analysts’ insights and adjust the information.

Illustrate

Flow diagrams, mind maps, and graphs are irreplaceable tools for explaining the connection between different features in software. It’s easier to understand the complex relationships within a system by looking at a mind map rather than reading long sentences.

Ask For Feedback

Software engineering isn’t just bare functionalities. Remember, there is always a bigger picture with business goals. Remember, SRS writing is a team play of developers and stakeholders, so make negotiation a habit.

SRS Writing Instruction

Finally, let’s dive into SRS preparation. The Asana template may come in handy.

Make an Outline

A typical SRS begins with a title and an outline. We recommend inserting links into outline topics – it will be easier to surf through the document.

  1. Introduction

1.1 Scope

1.2 Value

1.3 Target audience

1.4 Use cases

1.5 Product overview

2. Functional requirements

3. External interface requirements

3.1 User interface requirements

3.2 Hardware interface requirements

3.3 Software interface requirements

3.4 Communication interface requirements

4. Non-functional requirements

5. Glossary

 Introduction

Think about the main purpose of the product and include it in the document.

Scope

Make a list of business goals and objectives.

Value

What benefit will the product give to your customers? It’s a suitable section to mention the unique selling point (USP) and think how your product stands out on the market.

Target audience

To nail the target audience description, involve business analysts and create an end-user profile. Incorporate it into the SRS document – it will help to create use case scenarios later.

Use case scenarios

Write how customers will use the software. Sometimes it’s relevant to include user interface interactions as well.

General description

Describe the functionality of the software from the bird-eye view to provide a general context.

Describe Functional Requirements

Be as precise as you can here. Measurable and specific requirements help developers a lot. Don’t forget about visuals and include them in your paper.

Check some examples for a better understanding of functional requirements:

External Interface Requirements

  • Describe how users interact with the software (screen layouts, style guides, etc.).
  • The software will run on different devices, so provide the list of them. Mention network requirements and communication protocols.
  • Mention the connections between your product and other software components, including frontend/backend framework, libraries, etc.
  • List any requirements for the communication programs your product will use, like emails or embedded forms.

Describe Non-Functional Requirements

Think of the system’s work character and user experience. Include some external constraints that impact your software.

Five examples of non-functional requirements:

Category / Example

  • Speed / Search engine results
  • Security / Protecting sensitive ticket data in the airplane system
  • Transportability / The app’s performance on different devices
  • Reliability / Failure rate forecast
  • Usability / Intuitive UI design where users can predict what any button does
  • Capacity / Storage capacity in gigabytes

Add Glossary

Besides other details that you may add, a glossary is a must-have, as it explains all the terminology. A glossary saves time and cost, leaving no space for misunderstanding.

Present The Draft

As we mentioned before, requirements engineering is teamwork. Once you crafted a draft, invite stakeholders and initiate a discussion. It’s the chance to revise, propose some changes, and come to a common agreement.

How to Create Use Cases

Step 1. Imagine all possible interaction paths between each end-user and a system.

Step 2. Describe how the system will react in detail. Remember how we promised the end-user profile would come in handy? This section is a star time for it. Break it down into separate users and imagine individual use cases for them.

Step 3. Work on alternative scenarios – you can draw a tree of interaction for better visualization.

Step 4. Identify a pattern among users and document it separately.

P.S.: Don’t forget to include the administrators as system users in this section.

Great SRS Checkbox

While preparing the SRS document, remember the characteristics that will make a great requirements file. Explore additional features.

Space For Implementation Constraints

Sometimes the success of software engineering depends not only on the development team but also on the services used in the process. With that in mind, a great SRS should be detailed and leave space for casualties from third parties.

Accurate

This blog has already mentioned the importance of clarity in the document. Check your software requirements specification for accuracy and evaluate the quality of functional and non-functional requirements.

Remember, if the feature description is clear, it doesn’t leave space for subjective interpretations.

Flexible

Remember about possible iterations in the product development and treat the SRS as a flexible file, not a sturdy rule book. Don’t be afraid to leave some space for future updates!

Accessible

Stakeholders and the development team must be able to view and comment on the software requirements specification. Make sure everyone involved has easy access to the document.

Logical

The SRS documentation parts have to be consistent and complementary. If the purpose is “to serve customers a quick shopping experience”, but an ordering process requires the client’s maiden name to buy a dress, there is something wrong. Double check the document and eliminate any inconsistency.

SRS and Development Lifecycle

  • Waterfall
  • Agile
  • Scrum

Waterfall

A waterfall lifecycle is a step-by-step project management system. Development stages form a chain that doesn’t change in a process and follows one another.

Waterfall

The SRS documentation writing process stands as the first phase in this model. There are a couple of pros and cons of the waterfall method relating to software requirement engineering.

 Pros

  • The stages don’t overlap and are easy to follow.
  • Each phase is completed on time.
  • It’s easy to evaluate the results because every stage has specific objectives.
  • The waterfall method benefits short-term projects with little or no risks of change management in the process.

Cons

  • There is no place for flexibility to change requirements when the first stage is completed.
  • It’s hard to test the features early, as the minimum viable product (MVP) is developed late in the project.
  • It doesn’t fit long-term or high-risk projects, where change is inevitable.

Agile

SRS creation in agile projects is somewhat different. First, the software requirement specification is a 100% living document in this project management system because requirements can be added or changed within each iteration.

Secondly, the document looks more like software capabilities at the moment of every iteration instead of a list of requirements. Sometimes, agile teams don’t have a traditional-looking SRS, but acceptance testing and user stories are created at each module with the help of business analysts.

Scrum

Scrum is an Agile method that uses iterative work form. However, because it focuses on giving constant value to clients in separate short time periods based on feedback, the requirements change constantly and are usually unknown at the beginning of the project.

So how does this influence SRS documentation? Great question!

Actually, there are several Scrum artifacts (documents) that contain software requirements. They are product backlog, sprint backlog and sprint burndown chart.

  • Product backlog: contains documented user stories which are the main source of requirements.
  • Sprint backlog: сontains tasks for the team for each sprint. The tasks are formed from the product backlog list.
  • Burndown chart: the tracking instrument of the team’s progress.

Instruments For SRS

  • Microsoft Word and Google Docs
  • Jira
  • Perforce Helix RM
  • Pearls
  • ReqSuite RM

Microsoft Word and Google Docs

The simplest and the most common instruments for requirements management are MS Word and Google Docs. These tools are commonly used in low-budget projects, and their simplicity isn’t worth the consequences. On the one hand, it may seem they save money when in reality, they slow down the requirements gathering process, don’t provide requirements traceability, and it’s probably impossible to lead the long-term complex project with these instruments.

Due to digital transformations in document management, there are plenty of advanced tools for creating and organizing software requirements specifications.

Jira

Jira is intended for project management, however, it’s possible to use it as a requirement-gathering tool. The Atlassian support page offers to combine Jira and Confluence for SRS writing, as well as other apps on its marketplace (for instance, R4J and RMsis).

Jira has features to create issue types, sub-tasks to add and delete requirements and link them together in the document.

Perforce Helix RM

Perforce Helix RM is another tool that can be used as an additional software for Jira, Slack or GitHub. You can track, review and decompose requirements. There is a built-in testing feature that is built with machine learning and cuts the manual work. It’s convenient to use this tool for tracking requirements approval and change. For better development scheduling you can benefit from impact analysis as well.

Pearls

The strong side of Pearl is the ability to generate the SRS document in one click once the requirements are gathered. Besides, it offers a cool team management system that includes comments and shared access.

ReqSuite RM

ReqSuite is highly rated among RM products and has some advantages over other tools:

  • AI smart assistance
  • Intuitive interface
  • Reports
  • Customization
  • Premium support

Summary

The main idea that we wanted to deliver by this blog is that the software requirement specification document is crucial for any team of any project management framework. The forms of the file may differ, as well as the rigor of given requirements, but without the SRS document, any project is bound to fail and not bring value on the market. If your company is determined to succeed, then you definitely should work on SRS documentation.

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