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Introduction to Functional Requirements
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Today, we'll dive into functional requirements. What do you think they are? Can someone define them?
I think functional requirements describe what the system should do.
Exactly! Functional requirements detail specific behaviors and services the system must provide, answering the question: 'What should the system do?' Example statements might include 'The system shall allow users to register an account.' Remember, they are often action-oriented.
Does every functional requirement have to be testable?
Good question! Yes, they should be testable. For instance, if a requirement states 'The system shall generate a report,' we should be able to test if the report is indeed generated successfully.
Can you give us more examples of functional requirements?
Sure! Examples include 'The system shall allow users to reset their passwords' and 'The system shall display user profiles.' Letβs summarize: FRs specify actions related directly to user goals and must be clear and testable.
Introduction to Non-Functional Requirements
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Now letβs shift to non-functional requirements. How would you define them?
I think they describe how well the system should perform its functions.
Correct! NFRs define the quality attributes of the system, addressing aspects such as performance, security, and usability. They answer the question: 'How well should the system perform?'
Can you provide some examples of non-functional requirements?
Absolutely! For example, an NFR might state 'The system shall be available 99.99% of the time.' Another could be 'The system shall load the homepage within 3 seconds.'
Why are these requirements so important?
NFRs are crucial because they impact user satisfaction, system performance, and architectural decisions. High-quality NFRs can lead to a successful product. To summarize, NFRs ensure the system meets performance standards and provides a good user experience.
Comparing Functional and Non-Functional Requirements
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Letβs compare functional and non-functional requirements. How might we differentiate them?
FRs are about what the system does, while NFRs focus on how well those functions are performed.
Exactly! FRs state the functionality, while NFRs outline quality measures. Both are essential for software success.
Is it possible for a functional requirement to also have a non-functional aspect?
Absolutely! For example, 'The system shall allow a user to submit a form' is a functional requirement. If we add 'and do so in under 2 seconds', we've introduced a non-functional aspect. Remember, they often work together to ensure a system meets overall goals.
So, they are interdependent?
Yes, they indeed are! Effective software requires the interplay of both FRs and NFRs. In conclusion, while FRs focus on capabilities, NFRs govern performance and quality.
Introduction & Overview
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Quick Overview
Standard
In this section, the distinction between functional requirements (FRs) that describe what the system should do and non-functional requirements (NFRs), which outline how well the system performs its functions, is thoroughly explored. A well-rounded understanding of both types of requirements is essential for designing high-quality software systems.
Detailed
Differentiating Functional and Non-Functional Requirements
Overview
In software engineering, requirements are classified into two primary types: functional and non-functional. Functional Requirements (FRs) detail the behaviors, functions, or services the system must provide to its users, clarifying what tasks the system should accomplish. Conversely, Non-Functional Requirements (NFRs) define the quality attributes, performance criteria, and constraints on the system, guiding how functions should be performed rather than focusing on the functions themselves.
Functional Requirements (FRs)
Functional requirements primarily answer the question βWhat should the system do?β They are action-oriented, articulated often using verbs such as "shall allow" or "shall calculate". Each requirement should directly relate to user tasks, ensuring the system meets its core objectives. Examples of FRs include:
- The system shall allow a registered user to log in using their valid username and password.
- The system shall calculate the total price of items in the shopping cart, including applicable taxes.
Non-Functional Requirements (NFRs)
In contrast, non-functional requirements address βHow well should the system perform?β These requirements are crucial for user satisfaction, impacting the overall success of the system architecture. Categories of NFRs include:
- Performance: e.g., The system shall load the dashboard within 2 seconds for 90% of users.
- Security: e.g., The system shall protect against SQL injection attacks.
- Usability: e.g., A new user shall be able to complete their first order within 5 minutes.
NFRs often have a significant influence on system architecture and design, making them essential considerations during the requirements phase.
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Understanding Functional Requirements (FRs)
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1.1. Functional Requirements (FRs):
Definition: These describe the behaviors or services that the system must provide to the user or to other systems. They specify what the system does. They are directly tied to the business processes and user tasks the system aims to support.
Characteristics:
- Action-Oriented: Often expressed with verbs like "shall allow," "shall calculate," "shall generate," "shall display."
- Directly Related to User Goals: Each FR typically helps a user achieve a specific objective.
- Testable: Generally straightforward to test by checking if the specified function performs as expected (e.g., a test case for "User Login" passes if the user can log in correctly).
Examples:
- "The system shall allow a registered user to log in using their valid username and password."
- "The system shall calculate the total price of items in the shopping cart, including applicable taxes."
- "The system shall generate a printable invoice for completed orders."
- "The system shall display a list of available products filtered by category."
Detailed Explanation
Functional Requirements (FRs) specify what the system should do. They focus on providing the necessary functionality to fulfill user tasks and business processes. FRs are action-oriented, often using phrases that indicate the actions the system should perform. For instance, if an online shopping platform states, 'The system shall allow a user to add items to a cart,' this is a direct instruction about the behavior expected from the system. Additionally, FRs must be testable, meaning that once the software is developed, one should be able to confirm that the requirement is met through testing.
Examples & Analogies
Imagine a coffee shop where the owner defines exactly what services the staff should provide: making coffee, serving pastries, and taking orders. Each of these tasks represents a functional requirement for the coffee shop's operation. Similarly, in software development, when a team identifies that the software must log user activity or allow users to upload files, these tasks represent functional needs that guide the development team.
Understanding Non-Functional Requirements (NFRs)
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1.2. Non-Functional Requirements (NFRs) / Quality Attributes / Constraints:
Definition: These describe how well the system performs its functions, or the quality characteristics it must possess, or the constraints under which it must operate. They specify the system's qualities, rather than its specific behaviors.
Impact: NFRs often influence the system's architecture and design far more profoundly than FRs. They are crucial for user satisfaction and system success.
Categories and Examples:
- Performance: Response time ("The system shall load the dashboard within 2 seconds for 90% of users.")
- Security: Authentication (login), authorization (access control), vulnerability resistance ("The system shall protect against SQL injection attacks").
- Usability: Learnability ("A new user shall be able to complete their first order within 5 minutes.").
- Reliability: Availability/Uptime ("The system shall be available 99.99% of the time.").
- Scalability: ("The system shall scale to support 1 million concurrent users without significant performance degradation.").
Detailed Explanation
Non-Functional Requirements (NFRs) focus on how well the system should perform its tasks rather than the tasks themselves. These requirements define the quality attributes of the system, such as how fast it should respond, its security features, and how easy it is to use. NFRs are essential because they set the performance baseline and user experience expectations that functional requirements, while crucial, cannot fully encompass. For example, specifying that a system must be secured against cyber attacks is as vital as specifying what the system should do, as security can determine whether an application is safe for users.
Examples & Analogies
Think of a car where functional requirements describe what it can do, such as speed and fuel efficiency (e.g., 'The car can travel 60 miles per hour'). In contrast, non-functional requirements would discuss how comfortable the ride should be, how quiet the engine operates, or how safe it must be (e.g., 'The car should not exceed 60 decibels at 55 mph'). Both requirements are essential to ensure that the car not only performs adequately but also provides a positive driving experience.
Contrasting Functional and Non-Functional Requirements
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1. Differentiating Functional and Non-Functional Requirements: The "What" vs. the "How Well"
While functional requirements focus on what the system must do, non-functional requirements focus on how well those functions must be performed. This distinction is crucial as it influences system architecture and user satisfaction. Understanding both types is essential for the overall success of software projects.
Detailed Explanation
This section emphasizes the difference between functional and non-functional requirements. Functional requirements answer the question of what the software should do, citing specific capabilities like data processing or user interactions. On the other hand, non-functional requirements clarify how efficiently or effectively these functions should operate, focusing on areas like speed, security, and usability. Both are critical for comprehensive requirements understanding, as failing to adequately specify either can lead to software that meets functionality expectations but fails under quality metrics, or vice versa.
Examples & Analogies
Imagine ordering a pizza. The functional requirements would detail the pizza's toppings, size, and preparation (e.g., 'The pizza should come with pepperoni and cheese'). However, non-functional requirements would include the delivery time (e.g., 'The pizza must arrive within 30 minutes'), the packaging quality, or the pizza's temperature upon arrival. Both sets of requirements are necessary for a satisfying customer experience.
Definitions & Key Concepts
Learn essential terms and foundational ideas that form the basis of the topic.
Key Concepts
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Functional Requirements: Describe the actions and functions a system must perform.
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Non-Functional Requirements: Define the quality attributes and performance criteria of the system.
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Performance: A non-functional requirement category related to system responsiveness.
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Usability: A measure of how user-friendly a system is.
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Security: A non-functional requirement that ensures data and system protection.
Examples & Real-Life Applications
See how the concepts apply in real-world scenarios to understand their practical implications.
Examples
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An example of a functional requirement: 'The system shall enable users to create an account.'
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An example of a non-functional requirement: 'The system shall be able to handle 1,000 concurrent users without performance degradation.'
Memory Aids
Use mnemonics, acronyms, or visual cues to help remember key information more easily.
π΅ Rhymes Time
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To function well is what FRs pulse, it's what the system does without a pause.
π Fascinating Stories
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Imagine a restaurant where functional requirements are the menu items (what they serve), while non-functional requirements are how fast the food is served and how clean the tables are.
π§ Other Memory Gems
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For remembering functional vs. non-functional requirements: 'FR is for Functions, NF is for Noise-free performance β how well they work.'
π― Super Acronyms
FR & NFR
- F: = Functionality Required
- N: = Non-negotiable Fidelity in performance.
Flash Cards
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Glossary of Terms
Review the Definitions for terms.
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Term: Functional Requirements
Definition:
Requirements that describe specific behaviors, functions, or services that a system must provide to its users.
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Term: NonFunctional Requirements
Definition:
Requirements that outline the quality attributes, performance criteria, and constraints under which the system must operate.
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Term: Performance
Definition:
A non-functional requirement category that specifies response times and throughput for the system.
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Term: Usability
Definition:
A non-functional requirement category focused on how user-friendly and efficient the system is.
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Term: Security
Definition:
A non-functional requirement that addresses the protection of data and resources within the system.