What is Requirement Specification: A Comprehensive Guide

Requirement specification is a cornerstone of successful project development. This process, crucial in fields like software engineering, clearly defines project goals and sets the stage for efficient execution. But What Is Requirement Specification exactly, and why is it so vital? Let’s delve into the details.

Requirement specification, also known as requirements documentation, is the detailed process of documenting all system and user needs and constraints. This documentation must be precise, complete, comprehensible, and consistent, ensuring a shared understanding among all stakeholders. It follows requirements capture and analysis in the Requirements Engineering process, culminating in a Requirements Specification document. This document dictates the design, verification, and maintenance of the product, containing all requirements and related information.

Understanding System and User Requirements

To fully grasp what is requirement specification, it’s essential to differentiate between system and user requirements.

System Requirements: These are detailed expansions of user requirements, acting as a starting point for new system designs. They provide a comprehensive description of how the system will satisfy user needs.
User Requirements: These are a combination of functional and non-functional requirements, written in simple language for easy understanding by users without technical expertise. The document should avoid technical jargon, system design details, or formal notations, utilizing simple tables, forms, and diagrams instead.

Functional vs. Non-Functional Requirements: Key Differences

Within user and system requirements, we find two distinct categories: functional and non-functional requirements. Understanding these differences is key to understanding what is requirement specification.

Functional Requirements: These describe the specific functions the system must perform. They detail what the system will be and how it will function to satisfy user needs. They describe how the system should respond to commands, its specific features, and what users can expect it to do.
Non-Functional Requirements: These outline the limitations and constraints of the system. They don’t directly impact the application’s functionality but define how the system performs. These are often sub-classified into categories such as:
- User Interface
- Reliability
- Security
- Performance
- Maintenance
- Standards

Alt text: Diagram illustrating examples of non-functional requirements for a software system, including security, performance, usability, and reliability.

While functional requirements specify what a system should do, non-functional requirements describe how the system will do it. For example, a functional requirement might state, “The application shall provide a list of connected users.” A non-functional requirement might specify, “The system shall only operate on Windows and Linux operating systems.” A system can’t function without meeting functional requirements, but it can still deliver the desired outcome without fully satisfying all non-functional requirements.

Benefits of a Well-Defined Requirements Specification

Having a clear and comprehensive requirements specification offers numerous advantages:

Shared Understanding: Ensures all stakeholders have a common understanding of the system to be developed, preventing misunderstandings later in the development process.
Reference Point: Serves as a central reference for all stakeholders throughout the development lifecycle.
Early Gap Identification: Helps identify any gaps or inconsistencies in the requirements early on, saving time and resources.
Reduced Costs and Time: Reduces overall development costs and time by minimizing rework due to requirement changes and misinterpretations.

Standards for Writing Effective Requirements

The Easy Approach to Requirements Syntax (EARS) methodology is an effective standard. EARS emphasizes clear, concise, and understandable language, improving the requirements engineering workflow. Key principles of EARS include:

Complete Sentences: Each requirement must be a complete sentence, avoiding bullets, acronyms, abbreviations, and jargon. Keep sentences short, direct, and complete.
Proper Structure: Each requirement needs a proper subject, predicate, and verb. The subject is the user or system. The predicate outlines the conditions, actions, or desired results. Use “shall,” “will,” and “must” to indicate necessity, and “may” to indicate optionality.
Clear End Result: Each requirement must effectively explain the desired end result from the system.
Measurable Quality: The requirement must describe the expected quality of the system, enabling measurement of the end result to verify proper implementation.

Types of Requirements Specifications

Various types of requirements specifications exist, each focusing on specific aspects of the system. These include:

Functional Requirement Specifications (FRS): Documents the functions a system must perform, including functionalities, premises, security measures, and other relevant information. Essentially, an FRS contains everything a system should do.
Performance Requirement Specifications (PRS): Captures all performance-related aspects of a system, such as response time, data throughput, efficiency, and scalability. Focuses on quantifiable and improvable aspects.
Configurations Requirement Specification (CRS): Documents all information related to system configuration, including supported platforms, software/hardware dependencies, and minimum system requirements.
Business Requirement Specifications (BRS): Captures all business-related aspects of a system, including user management, security, and data integrity. Covers anything that affects business operations.
Reliability Requirement Specifications (RRF): Documents all information related to system reliability, including uptime, recovery time, and error rates.
Compatibility Requirement Specifications (CRF): Captures information related to system compatibility, including supported platforms, software/hardware dependencies, and minimum system requirements.
Software Requirement Specifications (SRS): Documents all software-related aspects of a system, including functionality, performance, and scalability. Covers anything that affects software operations.

Alt text: Table comparing Business Requirements Specification (BRS) and Software Requirements Specification (SRS) based on definition, derivation, creator, level of detail, scope, and use cases.

Software Requirement Specification (SRS) vs. Business Requirement Specification (BRS)

It’s important to distinguish between the Software Requirement Specification (SRS) and the Business Requirement Specification (BRS). While related, they serve different purposes.

The SRS focuses on what the system must do, outlining the functional and non-functional requirements of the software. The BRS, on the other hand, focuses on why the system is needed and how it will be used, capturing the client’s needs and business-related aspects.

Feature	Business Requirements Specification (BRS)	Software Requirements Specification (SRS)
Definition	Describes requirements provided by the client/stakeholders.	Specifies functional and non-functional requirements of the software.
Derivation	Derived from client’s requirements and interactions.	Derived from the Business Requirements Specification (BRS).
Creator	Created by a business analyst.	Created by a system analyst, system architect, or business analyst.
Level of Detail	Describes functional specifications at a high level.	Describes both technical and functional specifications at a high level.
Scope	Deals with business requirements.	Deals with the resources the company provides.
Focus	Defines the customer’s needs and is used from project inception to completion.	Describes how the business functions when using the software or application.
Inclusions	Tables and use cases are typically not included.	Tables and use cases are included.

Key Characteristics of a High-Quality SRS Document

A good SRS document should possess the following characteristics:

Precise: Easy to understand, leaving no room for misinterpretations.
Measurable: Requirements must be measurable to validate and certify the final product.
Complete: Includes sufficient information for development and testing teams to complete the product and ensure it meets user requirements.
Feasible: Requirements reflect the actual state of affairs, considering cost, timeline, and technology.
Flexible: Adaptable enough to accommodate changes in the workplace.
Verifiable: Accessible to everyone on the development team for reference.
Consistent: Requirements are compatible and do not contradict each other.
No Implementation Constraints: Detailed enough to guide development without overly restricting it.
Accurate: Requirements are precise, avoiding loopholes, ambiguities, subjectivity, or comparisons.

Essential Components of a Software Requirements Specification

The main sections of an SRS typically include:

Business Drivers: Explains why the customer wants to build the system, including problems with the current system and opportunities the new system provides.
Business Model: Discusses the business model the system will support, including organizational and business context, main business functions, and process flow diagrams.
Functional and System Requirements: Details requirements organized in a hierarchical structure, with functional requirements at the top level and detailed system requirements as sub-items.
System Use Cases: Includes a Unified Modeling Language (UML) use case diagram explaining key external entities interacting with the system and their use cases.

Alt text: Visual representation of a business model highlighting key aspects such as customers, value proposition, channels, customer relationships, revenue streams, key activities, key resources, key partnerships, and cost structure.

Technical Requirements: Discusses non-functional requirements, the technical environment, and technical limitations.
System Qualities: Defines the system’s qualities, such as reliability, serviceability, security, scalability, availability, and maintainability.
Limitations and Assumptions: Describes limitations imposed on the system design and assumptions made by the engineering team.
Acceptance Criteria: Details conditions to be met before the system is handed over to the final customer.

Structure of a Comprehensive SRS Document

A well-structured SRS document typically follows this format:

1. Introduction

1.1. Purpose: Explains the SRS’s objective and structure, including the types of requirements and the intended audience.
1.2. Intended Audience: Specifies who will use the SRS, such as product owners, investors, business analysts, developers, testers, and operations staff.
1.3. Intended Use: Describes scenarios where the team will use the SRS, such as designing features, planning projects, estimating costs, evaluating risks, and resolving conflicts.
1.4. Scope: Outlines the product’s scope, including its primary purpose, function, and position, detailing user types and key architecture components.
1.5 Definitions and Acronyms: Provides definitions for key terms, technologies, personas, and business entities to ensure clarity.

2. Overall Description

2.1 User Needs: Lists the problems the system will solve for users, categorized for segmented audiences.
2.2 Assumptions and Dependencies: Highlights the team’s assumptions about the product and its capabilities, allowing for focused development on essential features.

3. System Features and Requirements

3.1 Functional Requirements: Details the functions the system will carry out, prioritizing features based on their importance to the application.
3.2 External Interface Requirements: Describes the external interfaces, including the user interface, software interface, hardware interface, and communication interface, specifying the page elements visible to the end client.
3.3 System Requirements: States the conditions under which the product can be used, pertaining to hardware specifications and features, often defined by minimal, maximal, and optimal ranges.
3.4 Non-Functional Requirements: Defines how effectively the system must operate, establishing criteria for performance, security, and usability, with quantifiable scores assigned to each requirement.

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If you’re looking for a requirements management tool that will help you with both functional and non-functional requirements, consider Visure Requirements. This platform allows you to create, manage, and track all your project’s requirements in one centralized location.

Conclusion: Embracing the Power of Requirement Specification

Understanding what is requirement specification and implementing it effectively is crucial for project success. A well-defined requirement specification ensures clear communication, reduces risks, and ultimately delivers a product that meets the needs of all stakeholders. By adopting best practices and leveraging tools like Visure Requirements ALM Platform, organizations can streamline their requirements management process and achieve better project outcomes. Request a free 30-day trial at Visure Requirements ALM Platform to see how our tool can help your projects run more smoothly.