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Starting a software development project is an enormous and intimidating endeavor that may seem overwhelming at first. To simplify the preparation, companies acquire BA services to generate functional and nonfunctional requirements. These constitute a master plan that your teams can follow throughout the entire project. In this article, we’ll discuss what are functional and nonfunctional requirements, mention some examples, and cover essential documents.

Types of Requirements

Before breaking down requirements into functional and nonfunctional, let’s discuss how types of requirements exist.

Functional and Nonfunctional Requirements

Business Requirements

Business requirements in software solely include statements associated with objectives and needs. Without delving into the technical specifics, business requirements address the overarching goals that the company is striving to achieve. For example, they can include an increase in revenue, cost reduction, or elevated customer experience.

Stakeholder Requirements

User requirements in software cover what stakeholders expect from your creation. Stakeholders include executive managers, other staff, and end consumers. This part is designed to merge business requirements with the more concrete solution specifications. Based on the goals you want to achieve and the expectations and needs of your stakeholders, you can begin conceptualizing an appropriate solution.

Solution Requirements

Solution requirements encompass specific characteristics of your future digital product. Comprising two large groups of functional and nonfunctional requirements, solution requirements entail the core of the entire project. While functional requirements describe what tasks the product should perform and how, nonfunctional requirements address the general system property—in other words, quality attribute.

Transition Requirements

Finally, transition requirements are short-term steps that a company needs to take to secure successful implementation. These could vary from employee training sessions to data migration. Basically, anything that needs to be accomplished before or during the project to prepare the organization for the new product.

Montel Energy App

Difference Between Functional vs Nonfunctional Requirements

In this section, we’ll elaborate on the difference between functional requirements vs nonfunctional requirements and attempt to identify the main types.

Functional Requirements Definition

Before dissecting functional vs nonfunctional requirements, let’s explore what they entail. Functional requirements define a set of features necessary to use the application. Any functions that are required to accomplish tasks and solve issues that the user has fall under this category. In other words, functional requirements encompass the features without which the system will not be usable.

Types of Functional Requirements

From authorization levels and interfaces to historical data and legal regulations, functional requirements encompass a wide range of features. The exact set of functions depends on the type of application you’re building. For example, a hotel management app should include a feature that allows guests to view the status of their booking, while a social media app requires a messaging function.

Let’s take a look at some prominent functional requirements types:

Input requirements describe the format and validation of user inputs and ensure the app can receive and understand the transmitted data. For instance, the system should be able to validate the input based on specific criteria and enforce restrictions whenever the input doesn’t meet certain parameters.

Output requirements define the results and responses the system should provide to a certain input. These include how the data is displayed—from reports, charts, and dashboards to notifications and alerts.

Process requirements refer to actions and steps the system follows to accomplish a certain task or request. For example, these requirements define the authentication process, calculations, ordering, inventory management, and other tasks the app is designed to perform.

Data requirements address the way the system deals with data, from aggregating and storing to managing and securing. The requirements describe data formats, types of databases and storage, security measures, and more.

Functional requirements are essential in software development as they define the specific features, behaviors, and capabilities that a software system must possess to meet the needs of its users. Here are some real-life examples of functional requirements across different domains:

Nonfunctional Requirements Definition

In functional vs nonfunctional requirements, the former describes what a system should do, while nonfunctional requirements address how it should perform. These requirements in software are meant to ensure that your application is responsive, fast, usable, stable, and efficient. Basically, nonfunctional requirements play a major role in user experience and can help your solution stand out.

Types of Nonfunctional Requirements

There are two types of nonfunctional requirements::

System qualities are requirements that focus on the system’s quality attributes. These qualities include a long list of nonfunctional requirements such as usability, security, reliability, capacity, and many others. Software architects are usually responsible for identifying and generating these requirements to build a powerful and user-friendly solution.

Design constraints are requirements that limit design options to secure the system. For instance, you may narrow down the list of vendors to ensure the best possible quality. Other examples extend to the choice of programming languages and frameworks, usage of open-source technology, and other constraints that may impact your design. Although the list of design constraints should be minimal, they are important for the system’s performance and safety.

Examples of Functional and Nonfunctional Requirements

Now that we’ve established the definitions and main categories of requirements, let’s take a look at examples. In this part, we’ll investigate functional and nonfunctional requirements examples.

Functional Requirements Examples

Basically, functional requirements can be separated into different features and functions that an app must perform. In this section, let’s break down which functional requirements are essential to businesses.

Functional and Nonfunctional Requirements

Input Requirements define how user inputs are captured and processed by the systems, including format and validation. The goal of input requirements is to establish an efficient capture and interpretation of data. Examples of input requirements are error handling and data processing. 

  • Data processing functional requirements describe how your software system collects, stores, and retrieves data based on your business rules. From data validation and calculation to data transformation, these requirements are created to safely and efficiently deal with data. 
  • Error handling functional requirements specify how the system detects and responds to errors to offer helpful and meaningful messages to users. Furthermore, this functional requirement chooses what information should be audited and debugged to prevent errors in the future.

Output Requirements describe the outcomes and responses of the system based on inputs. In other words, they specify how the system should react to deliver meaningful and useful outputs. Output requirements encompass reporting and UI/UX. 

  • Reporting functional requirements are necessary for certain types of systems. Based on available data and user requirements, they should be able to create various reports such as charts, graphs, dashboards, etc. For instance, these could be used to generate sales reports or analytics dashboards.
  • UI and UX functional requirements are designed to offer an intuitive and user-friendly interface that caters to your target audience. They concentrate on the app’s layout, navigation, design, and other visual characteristics.

Process Requirements address how the system should behave to achieve its goals. These requirements describe operations that the system must perform to deliver what it’s intended to deliver. Process requirements include user authentication, authorization, system integration, and transaction. 

  • Authentication functional requirements deal with identity verification and credentials like passwords and usernames, biometric data, and multi-factor authentication processes. The goal of this functional requirement type is to ensure that only authorized users have access to your systems.
  • Authorization levels functional requirements focus on access management and which users are privy to what type of information. This requirement specifies concrete criteria that determine whether a user can alter or delete data and to what extent.
  • System integration functional requirements can help your development team to tether other systems to your future product. They specify interfaces, APIs, and protocols to provide communication between systems. For instance, you can connect your application to a payment gateway to allow users to make purchases.
  • Transaction functional requirements deal with various transactions that take place within the system. They determine how the application would manage and process financial transactions and database updates. This type of functional requirement adheres to ACID properties which make sure the transactions are atomic, consistent, isolated, and durable.

Finally, data requirements define how data is stored and organized within the system. Data requirements include data backup and recovery.

  • Backup and recovery functional requirements provide measures to secure data from getting erased or lost. By determining the storage methods and retrieval mechanisms and frequency, you can create a safe and bulletproof recovery plan. This functional requirement defines a concrete strategy for restoring sensitive data as well as recovering the functionality of the system.

Nonfunctional Requirements Examples

What are functional vs nonfunctional requirements examples? In this part, let’s take a look at the most crucial nonfunctional requirements and determine their importance to the app’s performance.

Functional and Nonfunctional Requirements

Performance nonfunctional requirements determine the system’s efficiency and responsiveness. From response time and reliability to scalability and user capacity, this nonfunctional requirement defines how well the application will handle workloads, respond to requests, and meet other performance expectations.

Security nonfunctional requirements are designed to protect the system from unauthorized access. By ensuring data confidentiality and integrity, you can safeguard your solutions from breaches and attacks. This nonfunctional requirement includes data encryption, regular audits, compliance assurance, and other safety measures.

Usability nonfunctional requirements mainly focus on user experience. They are created to ensure the application is user-friendly, efficient, and intuitive for the customer base. For example, if your target audience includes people with certain disabilities, it’s vital to create an interface that accommodates that. Other requirements address design, error handling, response time, and learning curve.

Reliability nonfunctional requirements are intended to ensure the system’s functionality is consistent and failure-proof. The main goal is to identify acceptance criteria of system uptime, recovery capabilities, and fault tolerance.

Performance nonfunctional requirements specify the system’s response time, throughput, and resource utilization to ensure the highest levels of performance. This nonfunctional requirement addresses page load time, algorithm efficiency, and database query optimization.

Availability nonfunctional requirements deal with the system’s accessibility and potential downtime. For example, during regular maintenance, you need to ensure that the most critical components of the application remain available. Additionally, these nonfunctional requirements include the maximum tolerable downtime in case of emergency as well as user notifications.

Scalability nonfunctional requirements define how the system would grow or shrink without jeopardizing its functionality. To accommodate the growth, the application needs to be able to adapt to the changes in workload, traffic, and data volume. Scalability can be increased by adding more memory or disk space as well as by compressing data and optimizing algorithms.

Portability nonfunctional requirements handle the system’s ability to effectively run on various devices, operating systems, and platforms. For instance, if a user acquires a new smartphone, they should be able to use your application in full. This nonfunctional requirement involves responsive design, cross-platform usability, and device independence.

Capacity nonfunctional requirements describe the system’s capabilities to handle expected volumes of data, users, and transactions. These nonfunctional requirements address thresholds for system functionality and performance within normal app usage.

Testability nonfunctional requirements specify how the system should be designed to facilitate effective testing. These nonfunctional requirements include test automation, coverage, and data management.

Mobile App

Requirements Elicitation and Management

Elicitation of functional and nonfunctional requirements is a vital step in the software development life cycle process as it allows you to grasp what stakeholders expect from the solution. You can identify what issues they want to solve and what features will aid in covering their needs. By establishing a clear understanding of the project, its scope and objectives, you can ensure a transparent development process.

In a similar vein, functional and nonfunctional requirements management is a framework that ensures the development teams are aligned in their goals and understanding of deliverables. This is an ongoing process that allows you to tether project requirements and deliverables as well as enables clear communication with stakeholders.

Requirements Elicitation

Requirements elicitation is a process that allows companies to create a blueprint of the future product by defining the needs and expectations of stakeholders. Most commonly, business analysts are in charge of gathering functional and nonfunctional requirements with the help of data analysts, project managers, and product owners. The main difference between business analysts and data analysts is that the former are involved in business needs while the latter deals with the data itself.

The elicitation process consists of the following steps:

Functional and Nonfunctional Requirements

Identify Stakeholders

First, identify the stakeholders such as customers, managers, board members, project managers, developers, and any other people who are directly or indirectly involved in the project. Thorough user research is essential for this step as misidentifying the target audience can jeopardize the entire project. Your requirements should address the needs of all the stakeholders who are integral to the project’s success.

Elicit Requirements from Stakeholders

Once the stakeholders are identified, you can begin collecting information from them. There are a plethora of techniques companies use to gather information from various stakeholders, including brainstorming, focus groups, interviews, workshops, and surveys. Additionally, you can observe the stakeholders performing a particular action or process and document the findings. 

Document Your Findings

Based on the answers, put your findings on paper to create a functional and nonfunctional requirements elicitation document. Keep the information organized by needs, concerns, expectations, etc., to create a transparent and clear system.

Requirements Management

Requirements management is a process designed to ensure that all requirements are met and concerns are addressed. The process includes requirements prioritization, change management, traceability, and validation. Based on these parameters, you can estimate the project timeline and schedule, necessary human resources, and potential threats.

Once all the steps are completed, get approval from the stakeholders to make sure that everyone is on the same page. Finally, during your regular sprint retrospective meetings, monitor the progress of the project by tracking the deadlines, budgets, and milestones.

Essential Documents for Functional and Nonfunctional Requirements

Depending on the project, you may require a range of different documents and reports. From the mobile app requirements document and software technical documentation to user documentation, developers generate numerous records to monitor their projects. In this part, we’ll delve into specific requirements documents that help companies capture functional and nonfunctional requirements.

Software Requirements Specification Document

Software Requirements Specification (SRS) is a comprehensive document outlining functional and nonfunctional requirements in a software solution. It’s a structured document that serves as a blueprint for the entire project to allow stakeholders to gain a full understanding of what to build.

The main purpose of an SRS document is to define the scope of the system, describe functional and nonfunctional requirements, and provide details on design, development, testing, and validation.

A typical SRS document includes a brief introduction, system overview, functional requirements, nonfunctional requirements, and user interface properties. Additionally, it mentions system interfaces that elaborate on how the system interacts with external hardware, software, and databases. Finally, it identifies dependencies on external factors and provides a glossary to simplify the reading.

Why Create an SRS

A well-formulated SRS document facilitates better communication among stakeholders, eliminates misunderstandings and ambiguity, and enhances project planning. Furthermore, creating an SRS allows you to identify vital functional requirements and nonfunctional requirements and monitor their coverage throughout the project timeline. Finally, it serves as a great frame of reference for system validation.

Functional Decomposition and Work Breakdown Structure (WBS)

Functional decomposition is a process of simplifying complex systems into more manageable components and facilitates the creation of work breakdown structure (WBS). A WBS can be described as a tree-like structure that offers a simpler visual representation of the scope.

While building a feature may seem intimidating, if you break it down into smaller parts, the process will look more workable. You can begin with the overall project, identify the main deliverables, and then decompose each of them into smaller sub-deliverables. Continue to break down the scope until the parts cannot be isolated any further.

A WBS document is a convenient method of planning the project, ensuring proper resource distribution, and establishing milestones.

Why Document the Requirements

Documenting functional and nonfunctional requirements is highly important for the project’s success. From refining the scope and estimating the budget to aligning stakeholders, this step should not be overlooked. In this section, let’s discuss the core benefits of recording software requirements.

Functional and Nonfunctional Requirements

Avoid Mistakes

Putting your thoughts on paper creates a holistic overview and allows you to identify bottlenecks and threats before starting the coding process. Without a clear plan, you might exceed the budget, miss deadlines, or neglect to include crucial features and functions.

Stay within the Budget and Scope

Recording functional requirements and nonfunctional requirements can also help you prioritize the scope to stay within the predefined budget. Most likely, you’ll be able to cut some nonfunctional requirements due to their high costs and resources.

Anticipate Risks

Another benefit of keeping functional and nonfunctional requirements documentation is to forecast potential risks and threats to the system attributes. By carefully crafting a blueprint for the development processes, you can preemptively identify weaknesses and address concerns.


In nonfunctional requirements vs functional requirements, the former deals with the how and the latter with the what. While functional requirements allow you to formalize product features and functions of the solution, nonfunctional requirements aim to ensure the app’s performance, speed, and usability. If you’re interested in creating robust software, consider getting in touch with NIX. We’re a team of specialists who work across industries and offer end-to-end solutions. Our thorough approach delivers customer-oriented results and helps our clients build products they and their users need and want.

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