As a BA, your job is to protect value—to ensure that business sponsors get the results they expect. While you identify needs, define features, write use cases, uncover business rules and manage issues, don’t forget about the non-functional requirements!
Missing non-functional requirements can:
- Increase project risks
- Dramatically reduce stakeholder value
- Limit the productivity of internal and external users
- Create foundational defects that are difficult and expensive to fix
Defining non-functional requirements
- Describe the constraints or quality of the service/system/process/product as a whole or
- Describe constraints or quality measure of individual features or requirements.
Common categories of non-functional requirements include:
- Security -What requirements are needed to prevent misuse, keep unintended users out, authenticate users, keep data confidential to the appropriate users and non-users, and which actions can be taken by which users?
- Usability-Is the solution understandable to users? Do users intuitively know how to perform the action they want? Are there sufficient help resources or easily found contacts for help?
- Reliability & Efficiency-When does the system need to be available? What is needed to recover from errors effectively? What is the acceptable time for the system to perform certain functions?
- Transferability-Can the solution be used in other environments--technical or business? Does it need to be?
- Maintainability-What are the requirements around the ease of modifying the solution? How easy is it to add rules and logic, add users, change a component without impacting others?
- Compatibility-What other application, systems and solutions does the solution need to operate with?
Non-functional requirements example
An example always helps right? So, let’s use Angie’s Pizza Shoppe. They make most of their money delivering pizzas to busy downtown office workers during lunchtime. They want implement an online ordering system to minimize order errors and create efficient lunch delivery service. Check out these non-functional requirement examples:
|Non-Functional Requirement||System or Feature Level|
|The system shall provide a way to recover/view orders when the system is down||System|
|Scheduled system downtime should be between 3AM and 7AM.||System|
|The time it takes a user to place an order online should be equal or less than the amount of time it takes to place a phone order, which averages 5 minutes.||System|
|Credit card numbers should be hidden from all internal users except the general manager.||Feature|
|When entering credit card information the system needs to return an authorization/approval of valid card to the user within 10 seconds of submitting.||Feature|
|The system should work on mobile device platforms (Apple, Android) as well as desktops and laptops.||System|
|Angie’s Pizza Shoppe toppings vary by season. Internal users need to be able to modify the topping list daily, without a system release.||Feature|
Documenting non-functional requirements
Obviously, requirement deliverables vary widely across projects and organizations, but you need to find a way to:
- Elicit non-functional requirements from stakeholders
- Review/prioritize non-functional requirements with stakeholders
- Share non-functional requirements with sponsors, developers, testers, etc.
When determining the best way to document non-functional requirements for your project, remember that some will trace to the whole system and some will trace to features, user stories, or individual requirements. You might “document” the non-functional requirements by:
- Creating a separate non-functional requirement document
- Adding them to your requirement list denoting NFR in the “requirement type column”
- Listing them at the end of each use case
- Adding them to your user stories acceptance criteria
- Communicating these requirements verbally to the developers on your team
- Listing them on your process models and flow charts
Let’s not create devilish systems by ignoring non-functional requirements at the system whole or feature levels. Don’t assume your developers and testers understand system constraints or quality measures. Let’s be mindful of the value non-functional aspects of the solution bring to our users and stakeholders.
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