Software Design Document Vs Software Requirement Specificification - A Complete Guide

Software design document vs software requirement specification is a common topic to be discussed in software development. While both are highly important for any software development project, not knowing the basic differences may lead to various issues during the development process.

As per the recent statistics, nearly 70% of the projects fail to deliver what they are supposed to and the development process, strategies, and practices have a lot to do with this. It is important to know how to make SRS documents, and SRS designs, as well as understand the difference between requirements and specifications in software engineering.

This will also help you document each of them properly and utilize them in the right way. So, in this blog, we will guide you through all you need to know about software design documents vs software requirement specifications.

Understanding of Software Design Document (SDD?)

A software design document is defined as a written form of a report that includes all the vital information regarding the software design, architecture, and how to design it while meeting technical specifications. It is also known as a software design specification document.

A software design document is highly important as it specifies all the information related to the software design process, software design requirements, architecture, and others. It not only ensures that all the main software design requirements are met but also helps streamline the workflow of the software development team by guiding them through the right steps to build the software.

Also Read: Discovery Phase of Project: A Complete Guide

Understanding Software Requirement Specification (SRS)?

The software requirement specification or SRS document plays a very significant role in the software development process. A software requirement specification or SRS document is defined as a document that specifies all the details related to the software development process such as software development project scope, required features & solutions in the final product, functional & non-functional specifications, and maintainability, reliability, safety, resources, and others.

It is important to know how to make an SRS document as it simplifies everything by offering a detailed specification of all vital areas of software development. As a result, it becomes easier for the software developers to follow the right direction and meet the specific set of requirements in the final product.

Also Read: Mobile App Development - Step by Step Guide for 2022

Key Differences Between SRS and SDD

SRS and SDD are some of the most discussed topics in software engineering and software development. Now that you have a better knowledge of SRS design and software requirements let’s discuss in detail the difference between requirements and specifications in software engineering. There are a lot of factors which needs to be taken care of, lets talk about difference between srs and sdd.

Content

Content is the first thing that comes to your mind when knowing how to make an SRS document or how to write a software design document. The content for these two types of documents is completely different from one another.

An SRS document includes all the specification-related information of a software development project. The content of an SRS document is focused on the various areas of a project, such as -

• The outline of your software development project.
  
• The purpose of your software development project is like why it is being developed or the main reasons behind opting for that specific idea of product development.
  
• The description of your software from different perspectives such as operability, functionality, and others.
  
• The key functionalities of your software, what it is supposed to do, how it is supposed to execute specific tasks, etc.
  
• The performance of your software - the details specifications like its expected performance level, related KPIs (Key Performance Indicators), competitive factors like how well is it supposed to perform compared to the other similar products in the market, and others.
  
• The different non-functional properties that are expected from the product.
  
• The key external interfaces of the product and how will those interact with the other software or hardware, their key capabilities, and functionalities.
  
• The expected constraints to overcome during product development or key restraining factors while developing various features and solutions for the product.
  
• How will product development help you meet the overall business goals?
  
• The target audience or end-users of your product and how to cater to their requirements efficiently.

A software design document, on the other hand, includes all the details regarding the description of the software, how its features will be built, or how the product will be designed to meet the specific set of technical requirements. There are several pointers related to the design of your software that you need to include in a software design document, such as -

• The overall overview of the software development project mainly focused on the design and the stakeholders, along with the relevant information. This section should also include the title and the compact summary with the relevant information in simple-to-understand language so that everyone can utilize it.
  
• The context of your software development project and how to build the software efficiently to make it purposeful. This section of the software design document also specifies the key and useful metrics to measure the success of the software from various aspects.
  
• A comprehensive and relevant technical solution with proper details that can guide the software developers through the right steps to develop the right product.
  
• A detailed timeline guide that includes the milestones, time frame, and other relevant details so that the project team can know when and how to achieve the same on time.
  
  

Purpose

The main purpose of doing SRS design or knowing how to make an SRS document is, to provide the entire project team with a well-defined framework that they need to follow. It lists out the top software requirements needed to develop a project successfully while offering adequate information on the same. It is pivotal for not only the software developers but for the whole project team as it offers important insights on the operations, quality assurance, maintenance, key features and solutions to have in the product, and others. So, it is more like an informative guide for your software development team to ensure a successful product launch.

A software design document is more descriptive. It describes the complete design of the product or software the team is developing so that the developers can have a clear idea of exactly what is being developed. The main purpose of a software design document is to ensure the complete product design is achieved or that everything that is required in the software architecture and design is maintained. It not only helps the developers know in-depth about the expected software design but also describes how to design that, which architectural or project development approach can work the best etc. So, when it comes to knowing the difference between the requirements and specifications in software engineering, this factor remains a prime differentiator.

Method

In the software design document vs software requirement specification discussion, it is important to know the method followed to make each of them. To write an SRS document, you will need complete information on the project. Project scope, goals, features, functional requirements, etc. all information is vital for SRS design. The method involves going through the project requirement details as well as the overall project goals that are aligned with the business.

The software design documentation method, on the other hand, needs a more in-depth knowledge of the technical requirements, processes, system architecture, design development process, and the relevant tech stacks. Instead of the whole project and business perspectives, it is more focused on the whole software architecture design and the final design as per the requirements. And hence, the method of writing a software design document involves knowing the whole software design requirements, relevant technical process to follow, and other information. No doubt that the method of documentation is one of the top factors that help you understand the difference between requirements and specifications in software engineering.

Significance

The SRS document is highly significant in ensuring the product quality as well as the product features and solutions and how competitive they are in the present market. Not only the basic project scope, but all the other important areas such as the present market, competition, future growth scope, and others are taken into account during the SRS documentation process. So, it is highly significant in developing an efficient and competitive product for the present market as well as the one that can be a good fit as per the upcoming trends and demand as well.

The significance of the software design documents lies in the development of a complete product design that meets all the technical specifications. It ensures that the software design and architecture areas are required and efficient to deliver what the software is meant to. Also, a software design document is highly significant when it comes to the maintainability, scalability, and reliability of a product in the long run.

Also Read: Rapid Application Development (RAD): A Complete Guide

Why are both SRS and SDD essential?

Software Requirement Specification (SRS) and Software Design Document (SDD)  are both important components of software development process. There are many different purpose, but they work together to make sure that development is high-quality software.  

The SRS defines what the software should do. This gives a deteailed description of the system's functinality features, and business perpective as well. This document hepls briding the gap between the client's need and have a better understanding. This acts as a clear roadmap for developer, testers, and stakeholders to reference throughout the project, this ofcourse reduces the chances of misunderstandings or scope changes later.

On the other hand, the SDD explains how the software will be built. It provides a detailed technical blueprint, which includes the system architecutre, design patterns and even specific technologies to be used. The SDD helps the development team make better informed decisions about how to implement the requirements.

So, having both documents is essential because they cover different but aspect of the projects. The SRS makes sure that the right features are built, while the SDD make sure that those features are built correctly and efficiently.

Takeaway

Software design document vs software requirement specification is a widely discussed topic to explore. While both are an integral part of the software development process, it is crucial to know the differences to document them in the right way. The above guide will help you document the software requirements and software design properly and make the best out of it. All you need to know is the key differentiating factors and the main goals and purposes of such documents. However, based on your product development type, requirements, goals,m and other factors you need to focus on the documentation process.

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FAQs

1. Who is responsible for creating the SRS and SDD?
   
   The SRS (Software Requirement Specification) is typically created by business analysts and project managers, while the SDD (Software Design Document) is prepared by software architects or lead developers.
   
   
2. Why are both SRS and SDD important in software development?
   
   The SRS defines what the software should do, helping developers understand the project's needs. The SDD explains how the software will be built, making sure the technical design meets all requirements. Both documents guide the team in delivering a successful project. It gives you detailed information on requirements vs specification.
   
   
3. What tools can be used to create SRS and SDD?
   
   Common tools include Microsoft Word, Google Docs, Confluence, and Notion for documentation, as well as lucidchart or Draw.io for visualizing software architecture.
   
   
4. How do SRS and SDD affect software testing?
   
   The SRS helps testers create test cases to verify the software functionality, while the SDD makes the technical design is tested, making everything works as planned.