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How to Write a Product Requirements Document for Non-Medical Devices


Developing a brand-new product from the ground up is a big task. While there is a lot of support along the way, there are also many places where things can go wrong. Product development is a massively collaborative effort with a slew of moving parts contributing to the results.

To ensure that things go off without a hitch, you must develop a product requirements document, also known as a PRD.

This document is an integral part of the development process, ultimately guiding you, your team, and consultants as you turn a simple idea into a tangible product.

What is a Product Requirements Document?

A PRD is a detailed document that clearly defines a product's purpose, features, and functionality. Typically, product managers are responsible for writing the PRD, as it conveys critical information. However, any product development leader can take the reins to start the process.

While similar, the product requirements document is different from the marketing requirements document, which many refer to as MRD for short. The MRD comes before the PRD and focuses on the potential customer base. Writers develop this report from the perspective of the final user to define the needs and expectations of the target demographic.

Once that information is readily available, the PRD should be written from it. It serves as a roadmap for the development process and guides various teams on the journey to launch. While product managers write it, the PRD is a shared document that multiple stakeholders see. From the engineering team to lab specialists, every person contributing to the product's design uses the paper to guide their work.

When Do You Need a PRD?

As you can imagine, a well-written product requirements document is paramount. Any company developing a new product needs a PRD. Some may attempt to do without, but this leaves the team, or even an individual consultant, with ill-defined direction. It is critical that all team members are very clear about what needs to be done and what the product should be.

Think of it as the ultimate instruction manual. It doesn't provide step-by-step directions on building the product, but it can clear any confusion about functionality or component requirements. It's the document that every team must use to stay on the same page. Without it, you'll end up spending far too much time going back and forth between teams, manufacturers, and partners.

Product requirements tend to be more relaxed for non-medical devices, but it remains the same that each requirement must be testable and measurable for both medical and non-medical PRDs. Writing product requirements with care will result in less confusion, quicker approvals, and a much faster overall product turnaround.

There's no defined format for compiling the PRD. Technically speaking, managers are free to create unique systems to guide the development team. Many choose a spreadsheet-style format for the document. It's easy to read and utilizes common language to ensure that stakeholders at all levels can understand expectations.

Covering the Basics

Before getting into the product's functional requirements, the PRD should include an introduction with some basic information.

Start with a description of the device's purpose and scope. Cover why it's in the development pipeline and go over its intended behaviors. Write about the core functionality and expected features, so there is no question about what kind of product you're designing.

It's also a good idea to highlight how it fits into the corporate goals, initiatives, and strategies. As always, keep this introductory section precise and unambiguous. There should be no room for interpretation.


Establishing Functional Requirements

This section is the meat of the product requirements document. Here, you'll define functional requirements for every feature. Every requirement needs to be measurable and testable. These parameters will undergo strict scrutiny as they determine whether the product looks, behaves, and functions as it should.

The best way to keep the information organized and easy to read is by creating a spreadsheet. Each row should cover a single product requirement. For the columns, here are a few of the most common headings. See the example in this document.

  • ID

    This column acts as a quick-reference section. Your team will use the unique identification numbers to reference requirements internally. Make each ID distinct and easy to follow. Many product developers utilize a letter and number system. The letter can reflect critical systems or subsystems. For example, you might refer to an essential piece of hardware as H-001.

  • Component

    In the component column, define the high-level category of the requirement. IoT devices and wearables typically have multiple pieces or models. The component category makes it easier to differentiate conditions and stay organized. Some good examples here include Accessory or System.

  • Sub-Component

    In another organizational column, the sub-component defines the requirement even further. Typically, it reflects how the requirement implements into the high-level component. For example, you can distinguish if it's Hardware or Software.

  • Source

    Not every requirement will have a source. This column highlights any critical connections or additional reference documents. For example, one requirement might have an inherent connection to another.

  • Importance

    With this column, you're defining the importance of the requirement. Many developers use the "Shall/Should" language here. Putting "Shall" indicates that the requirement is a must-have. Meanwhile, "Should" shows your team that the requirement is preferred but not a top priority.

  • Requirement

    This section is the most important. It details the implementation target for each requirement. The language used here is what the development team will use for guidance. It's also the benchmark for testing later in the process.

  • Notes, Comments, or Questions

    The notes section is left blank initially. The PRD is a living document that other teams can modify as the product goes through the development process. Your engineers, architects, and testers will jot down notes or questions. Usually, findings that influence the implementation of the requirement will go here for later review.

  • Updated Comments

    Relevant teams will investigate comments in the notes section and put their findings or responses here.

Tips and Best Practices

Writing product requirements might seem relatively straightforward, but it takes time to complete this document correctly. Confusing or incomplete requirements could cause an endless loop of communications between teams or result in a product that is not what was desired.

Furthermore, it can make things harder for your lab testers. The goal of the PRD is to give your development team everything they need without ambiguity.

Here are some crucial tips to follow.

  • Be Specific

    Specificity is vital with product requirements. Avoid vague language and be precise.

    Instead of saying something simple like "The system shall deliver power to light the LED," you should fill in those knowledge gaps and provide exact data. A better requirement would be "The system shall deliver 0.5 watts of power to light the LED for three seconds."

    The more detailed the requirement is, the clearer it is for those developing the product.

    Also, use the reference column when necessary. Include any relevant requirements if dependencies exist.

  • Use Common Language

    Common language improves accessibility across the board. Not everyone on your team may understand highly technical jargon, but everyone plays an essential role in the product's development. Avoid confusion and keep things simple while remaining specific.

  • Make Everything Quantifiable

    Ditch qualitative requirements that don't use strict measurements. Every parameter should be quantifiable and repeatable. This document will guide lab testers, so subjective language and decision-making are out of the question. You don’t want the individuals on the project to make decisions about what was really meant.

  • Use Positive Terms

    In this case, positive terminology refers to how testers will measure the requirements. It's easier to prove that a product can do something than it is to prove that it can't. Once again, specifics are always preferred.

  • Avoid Duplicates and Contradictions

    Finally, proofread your document and make sure there are no contradictions or duplicates. Those will only add to the confusion and slow down your teams.

Starting Your Project on the Right Foot

It’s imperative to get your product requirements correct. Eliminate confusion from the beginning of the development process with a clear-cut goal that both Engineering and Marketing groups understand.

Voler Systems has decades of experience in writing and using PRDs, helping companies develop devices and bring them to market on time and on budget. Contact us today about your non-medical device project.

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