Functional and Non Functional Requirements

Summary

This transcript provides an overview of functional and non-functional requirements in system design. Functional requirements describe what a system should do, while non-functional requirements focus on how the system performs. It emphasizes the importance of clarity, testability, and feasibility in requirements, using user stories and the INVEST acronym for agile development. The script also discusses non-functional aspects like security, performance, scalability, and maintainability, and introduces tools like the requirements traceability matrix to track progress and ensure that the system meets its intended goals.

Takeaways

• 📝 Functional requirements specify what a system should do, focusing on inputs, behaviors, and outputs.
• 🔍 A good requirement is unambiguous, testable, feasible, independent, traceable, necessary, and implementation-free.
• 📚 User stories can be broken down using the INVEST acronym: Independent, Negotiable, Valuable, Estimable, Small, and Testable.
• 📱 An example of a user story is developing an iPhone application for issuing school permission slips.
• 📈 Non-functional requirements describe the quality of the user experience and system properties without altering functionality.
• 🔑 Security, performance, availability, and accessibility are examples of non-functional requirements.
• 🌐 Accessibility requirements ensure that systems are usable by people with disabilities, such as color blindness.
• 🛠️ Non-functional requirements also include system architecture, technology stack, and network considerations.
• 📊 Requirements can be categorized into must-haves, wants, and assumptions to prioritize and manage them effectively.
• 📋 A requirements traceability matrix helps maintain a master list of requirements and track their status and testing.

Q & A

What are functional requirements?

Functional requirements refer to the specific functions of a system or component, detailing the inputs, behaviors, and outputs, and clearly stating what the system should do.

What are the characteristics of a good requirement?

A good requirement should be unambiguous, testable, feasible, independent, traceable, necessary, and implementation-free.

What does the INVEST acronym stand for in the context of user stories?

INVEST stands for Independent, Negotiable, Valuable, Estimable, Small, and Testable, which are the characteristics that user stories should possess.

How can user stories be used to develop requirements for an iPhone application for school permission slips?

User stories can be written from the perspective of different users, such as 'As a principal, I want to run a report that identifies all completed permission slips so I will know which students can go on the field trip.'

What are non-functional requirements?

Non-functional requirements describe the qualities or attributes that the product must have, such as performance, usability, and security, without altering the product's functionality.

Why are non-functional requirements important?

Non-functional requirements are important as they help to describe the user experience and ensure the system meets certain standards of quality, even though they do not directly contribute to the system's functionality.

What is a common format for writing user stories?

A common format is 'As a [user role], I want [functionality] so that [value/benefit].'

How do non-functional requirements differ from functional requirements?

Non-functional requirements focus on the quality and constraints of the system, such as performance and security, while functional requirements specify what the system should do.

What are some examples of non-functional requirements?

Examples include response time, system capacity, data security, legal compliance, and system availability.

How can a requirements traceability matrix help in managing requirements?

A requirements traceability matrix helps maintain a master list of all requirements, tracks their status, and links them to test cases, ensuring that all requirements are delivered and tested as planned.

What are the categories of non-functional requirements mentioned in the script?

The categories include performance, availability, maintainability, capacity and scalability, and recovery.