The first step in software development is determining what you want to construct. This knowledge becomes apparent when you conduct market research, evaluate the advantages and disadvantages of rivals, comprehend customer wants, establish project objectives, choose app features, and draft a product roadmap during the discovery phase. You consequently have a clear idea of your product and how to construct it.

However, in most circumstances, you are not the only one working on the project. You have a team of committed designers, developers, QA engineers, and other experts. Furthermore, it's critical to make sure that everyone on your team understands what has to be built.

That is the purpose of both functional and non-functional requirements.

This article explains the distinction between non-functional and functional needs, the significance of these requirements for the effective development of software, and how to create them. In addition, we give several examples and outline our method for requirement elicitation.

What are requirements in software development?

One important component of the requirements that are typically developed for a software project is the combination of functional and non-functional needs. Let's first quickly review each kind of requirement in order to better grasp their function in software engineering. A Guide to the Business Analysis Body of Knowledge (BABOK) lists the following four categories:

• Business requirements outline the objectives and results that a product is expected to contribute towards.
• User requirements outline a product from the perspective of the user, outlining the features that software must have in order to meet the needs of users and advance organizational objectives.
• Solution requirements outline the features and functionalities a product must provide in order to satisfy user requirements. There are two categories of solution requirements: functional and non-functional.
• Transition requirements outline the short-term features and abilities a product needs in order to successfully undergo an update. Only when implementing changes are these prerequisites required. In other words, whereas business and user requirements explain why a client needs a product and how it will be used, solution requirements (also known as functional and non-functional requirements) describe which features to include in a product and how they should perform.

Every kind of requirement is interconnected. Understanding the business and user demands of your program, defining its functionality and the scope of work, carrying out functional decomposition, and prioritizing its features are all necessary before you can generate functional and non-functional requirements. You cannot create solution requirements or provide a detailed description of each feature until these tasks are finished. The process of gathering requirements is typically initiated in the project discovery phase, which is the first stage of developing software. Numerous businesses, including qadrtech, regularly use the Scrum framework, a collection of Agile project management practices and concepts, and operate their projects using the Agile approach. In this instance, requirements gathering goes on prior to each sprint throughout the delivery phase.

A large number of experts are involved in the collection and formulation of requirements. On the other hand, business analysts oversee the procedure and are skilled at translating a client's request into precise requirements documentation. Business analysts interact with clients, having conversations about their requirements, preferences, and expectations; they also prepare documentation and relay requirements to other team members, such as developers and QA engineers, as well as UI/UX designers.

Both functional and non-functional requirements are important for the successful creation of software. They not only help the development team as a whole comprehend what needs to be built, but they also assist with project estimation, risk mitigation, and other areas. How? Allow us to clarify.

Why is it important to form functional and non-functional requirements?

In software engineering, requirements act as an intermediary between the client and the development team. They help to: communicate the concept a client has in mind;

• Assure that every team member has a distinct vision for the software. All team members—UI/UX designers, frontend and backend developers, and QA engineers—can prevent misunderstandings about what needs to be done when system requirements are clearly stated and documented. The development process is more likely to go smoothly and effectively when everyone is aware of the exact features of the product they are going to construct.

• Give a precise estimate for the project's budget and schedule. Your delivery team can estimate the time needed for each feature's development, testing, and implementation and grasp the scope of work by having comprehensive knowledge about the functionality and quality standards that are needed. Your team may prevent missed deadlines and think of cost-saving measures for software development by defining reasonable timeframes and estimating software costs after requirements have been evaluated.

• Lower the possibility of project failure. Prior to the start of actual development, requirements elicitation gives you the opportunity to assess the project's technical viability, identify any discrepancies, select the best technology stack, and determine the organizational structure of the software development team. It's an excellent chance to confirm that all of the client's specifications are met and that developing the needed software is feasible. The team can operate more productively by defining functional and non-functional needs, understanding the client's expectations precisely, establishing reasonable timelines, and figuring out how to minimize risks.

Based on our personal experience, we can state that having well stated software requirements is crucial to satisfying customer expectations, improving user experience, and ultimately guaranteeing project success. Among the top 10 problems that lead to software development failure are unclear requirements and inadequate team communication. For this reason, gathering and recording functional and non-functional requirements early in the project life cycle is crucial. After learning about requirements elicitation's purpose in software development, it's time to respond to the following query: What are functional and non-functional requirements?

Functional requirements

You can grasp the general operation of your software when you decide on the scope of work, priority features, and business and user needs. In order to develop that program, though, you must thoroughly outline every feature. Functional requirements are meant for just that.

Let's say you wish to implement a chatbot for an AI SaaS product or incorporate a facial recognition feature into your mobile app. To make sure the developers understand your request completely, how should you communicate it to them? Examples of functional requirements for these features are as follows:

• In order to identify a person based on their facial features, the mobile app needs to ask for permission to access the device's camera.
• When LLM is implemented, after a user initiates interaction through text input, the AI chatbot needs to carry out predetermined tasks or actions based on the user's request. Stated differently, functional requirements define the features of software and the way it reacts to specific user inputs. They provide as recommendations for the software's functioning and design and lay the groundwork for future development.

What do functional requirements define?

You can specify how the system will behave under specific circumstances, commands, or inputs when you create functional requirements. There may be differences in the functional requirements for every feature. For instance, you might have to explain:

• Technical details on processes a system uses to perform its functions
• Data processing and management
• Interactions with external interfaces and systems
• Authentication levels, etc.

The kind of functional requirements you need to write will depend on the features of your system. Your objective is to provide a detailed description of every feature in your product so that your team knows what has to be developed to give users the functionality they want.

How to document functional requirements

The process of developing software is intricate, and every project includes a long list of specifications that specify the features that the program must have. Naturally, it isn't feasible to consider each of these at the same time when developing. You must so record the software prerequisites.

The kind of functional requirement definition document you use should primarily rely on the preferences of the team and the development approach (Waterfall vs. Agile). You can produce the following kinds of documentation to outline functional requirements:

• Software requirements specification (SRS). This comprehensive document includes not only functional characteristics but also a product overview, background information, limitations, and non-functional requirements. Business analysts frequently create software requirements specifications for projects that are executed according to the Waterfall methodology, but you can use an SRS for Agile software development as well.

• User stories and acceptance criteria. Typically used in Agile project management, user stories coupled with acceptance criteria allow you to understand who will use your product, for what, and what features are important to allow users to complete their tasks. Here is a common structure for user stories: As a [user role], I want to [do something] so I can [reason].

  As a customer, I want to add items to my wish list so I can find them quickly later.

  Acceptance criteria, in turn, serve as rules for features, specifying how exactly a feature should perform to be accepted by a user:

  A user should see an “Add to wish list” button near an item when viewing it.

• Use cases and scenarios. This documentation is used to describe user flows. While user stories describe what software should do, use cases describe how software should do it and what action a user should take to get the desired result. A use case includes a description, pre- and post-interaction system states, and all possible methods of interaction.

To define requirements and make sure the team and stakeholders understand them, there are several forms of documentation available. For instance, to reach a consensus on needs with a customer, we commonly depict requirements using flow charts, diagrams, and software prototypes.

Non-functional requirements

The objective of an app user is straightforward: utilize a feature to accomplish a particular result. When evaluating an app's functionality, we keep its functional requirements in mind. To make your app successful, you must also ascertain how well in-app features function when used. This guarantees an easy-to-use interface.

How quickly does a page load?

What user load should a system be able to handle?

To what standards should the app adhere to be secure for users?

You have to provide answers to these and a plethora of other questions in the form of non-functional requirements when getting ready for software development. They simplify things for the entire development team by providing context for how a system should operate in order to satisfy user expectations. You can steer clear of frequent product roadmapping blunders and make sure a system satisfies specific quality traits and limits by clearly defining non-functional requirements.

Types of non-functional requirements

Non-functional requirements: what are they? Non-functional requirements can be categorized based on the ways in which they represent the features and constraints of the system from various angles. Let's examine a few varieties that you might require for your project:

• Performance requirements (such as page loading time) specify how software should behave in different use cases and under different conditions.
• Usability requirements specify characteristics that make software easy to use for all types of users.
• Security requirements outline the legal and regulatory requirements a system should comply with to provide a secure user experience.
• Compatibility requirements outline what operating systems, hardware, and browsers software should be compatible with.
• Scalability requirements specify qualities software should have to perform well under increasing user demand.

It can be more challenging to define software restrictions and quality attributes than it is to provide functional requirements. To ensure that the team delivers a product that is both high-quality and satisfies the client's expectations, there are a lot of subtleties that you need to consider and record. Furthermore, non-functional qualities may be arbitrary or contradictory. For instance, since stringent security measures can impede a user's experience with your app by slowing them down, they may clash with usability needs.

It is improbable that someone without technical experience could formulate precise non-functional criteria. It is therefore preferable to work with a seasoned software development team. You can specify how your system should function to satisfy user expectations with the assistance of a business analyst, project manager, and software architect (or tech lead). In addition, a committed team will assist you in planning each step of the startup development process, guaranteeing a productive and easy development process.

How to document non-functional requirements

Whether an Agile or Waterfall software development technique is used will determine how non-functional requirements are documented.

Non-functional needs can be included in the software requirements specification (SRS), which is a document we previously discussed that also contains functional requirements, if you use the Waterfall process.

You can use the SRS for an Agile project or separately document functional and non-functional properties. For Agile projects, we find separate documentation useful because we typically use the Scrum framework, which values adaptability and flexibility over detailed documentation. As a project develops, we can more readily modify requirements when there is separate documentation. Thus, when non-functional requirements are documented differently from functional requirements, how should a Scrum team handle them? Technical stories and non-functional requirements lists are your two options. This is how they function:

• A non-functional requirements list is a simple but effective way to specify quality attributes of a system, where each list element defines certain conditions, qualities, and limitations a system should meet.

• Technical stories are similar to user stories but describe features not from the user’s point of view but from the system’s point of view. Let’s take as an example the following user story and create a technical story for it:

As a user, I want to search in an app so I can find people by their usernames.

The technical story for this example could be:

Search results update in real time on the page as a user types their request in the search bar.

Here, the technical story outlines the behavior of the system both during and following user input. For a single feature, there may be dozens of technical tales that cover every little aspect of how the system should operate in a given scenario.

It's also critical to note that requirements are developed prior to each sprint in accordance with the Agile methodology. Let's take an example where you wish to create a minimum viable product (MVP) initially. A business analyst develops both functional and non-functional requirements for a single feature and ranks the features for the MVP. As the first sprint gets underway, the team works on this feature. The business analyst develops requirements for a new feature for the following sprint, and so on, until all MVP functionality is completed. For the team to grasp the project's objectives, both functional and non-functional requirements must be well documented. Delivering comprehensive project parameters in the form of requirements documentation to your delivery team is essential, regardless of whether you're building the product yourself or hiring a software outsourcing business to execute it for you.

Functional vs non-functional requirements: What’s the difference?

The features of both kinds of requirements have previously been discussed extensively, so let's outline their main distinctions now. To help you identify the differences, we have provided a comparison of functional and non-functional requirements:

Here's an illustration of the differences between functional and non-functional needs.

Let's say you decide to begin creating an app using the SaaS business model. Since customers will have to subscribe in order to access your services, one of your app's features should let them buy and manage subscription plans. For this feature, let's outline the following functional and non-functional requirements:

• Functional:

  A user should be able to sign up for the service and manage their billing information in a subscription management system available from a sidebar navigation menu.

  This requirement adds clarity to your SaaS platform architecture and specifies what a user can do within the subscription system.

• Non-functional:

  A user’s personal information provided when starting a subscription must be encrypted according to security standards such as AES, DES, and RSA.

  This security requirement specifies how data provided by users in the subscription system should be protected to provide a secure user experience.

Requirements that are both functional and non-functional work well together. In the aforementioned scenario, having well defined functional and non-functional criteria will enable you to successfully design your SaaS service while meeting user expectations and offering a seamless, secure experience.

Functional and non-functional requirements elicitation: qadrtech approach

Every business approaches requirements elicitation differently. At qadrtech, we think that the most effective software development is possible when there is close client collaboration along with Agile project management. The following actions are part of our strategy:

1. Planning and preparation. We identify stakeholders, plan requirements elicitation activities, and choose techniques to gather requirements.
2. Gathering requirements. When we work on a project, a business analyst actively communicates with stakeholders, discussing their specific requirements and expectations. To identify stakeholders’ needs and expectations, we conduct one-to-one interviews, brainstorming sessions, and surveys. We can also prepare rough prototypes and show them to clients to identify misunderstandings and refine requirements if needed.
3. Documenting. We record all requirements in various formats. Starting with a work breakdown structure (WBS) and a business process diagram to define the scope of work, required functionality, and user workflows, we move to creating precise functional and non-functional requirements. The business analyst starts to create a product backlog that consists of user stories with acceptance criteria for functional requirements and technical stories for non-functional requirements.
4. Prioritizing. Our BA communicates with stakeholders to understand the importance of each feature and prioritize features. In this way, we organize our work to focus on critical features first. Before each sprint, documentation is produced gradually since we use the Agile methodology and work on product functionality in iterations, or sprints, rather than all at once. When a number of user stories are prepared, our BA reviews and refines each one with the client to make sure it meets the customer's needs and expectations. We prepare for a development phase in this way. Ensuring that requirements match the client's vision and goals is our primary objective. We continue to validate with the client not only user stories for new features but also functionality that has already been deployed, making sure the functionality that was produced in accordance with specifications truly satisfies the client's needs. We reduce the possibility of failure and prevent time and expense overruns by using this strategy.

Before gathering requirements, our team might carry out more project exploration activities if you only have an idea. We can assist you with market research, defining user demands and commercial objectives, confirming your idea through a proof of concept, and selecting the best approach to put it into practice.

Conclusion

Finding product-market fit is a topic that interests all businesses. It's a great idea to concentrate on what people need and anticipate from your app. You can then determine what features your software should offer. Communicating your software vision to developers is also crucial.

The development team can better understand what to construct and the outcomes you and your end customers expect when they have access to both functional and non-functional requirements. This is accomplished by providing thorough documentation that explains every software feature and its behavior in various scenarios.

Requirements elicitation happens early in the SaaS product lifecycle, typically during the exploration stage. Along with strong technical know-how, it calls for collaboration from the product owner, business analyst, and complete development team. Involving experts with pertinent experience is optimal for defining functional and non-functional product needs.

Get in touch with qadrtech if you're searching for a team that can assist you with selecting the features for your app, producing precise requirements documentation, and starting from scratch to develop a successful product! We want to know about your concept and assist you in putting it into action.