What is functional and non functional requirements?
Answers
Answer:
Functional requirements
1. Functional requirements specifies a function that a system or system component must be able to perform. It can be documented in various ways. The most common ones are written descriptions in documents, and use cases.
2. Use cases can be textual enumeration lists as well as diagrams, describing user actions. Each use case illustrates behavioural scenarios through one or more functional requirements. Often, though, an analyst will begin by eliciting a set of use cases, from which the analyst can derive the functional requirements that must be implemented to allow a user to perform each use case.
3. Functional requirements is what a system is supposed to accomplish. It may be
Calculations
Technical details
Data manipulation
Data processing
Other specific functionality
4. A typical functional requirement will contain a unique name and number, a brief summary, and a rationale. This information is used to help the reader understand why the requirement is needed, and to track the requirement through the development of the system.
Non functional requirements
1. Non-functional requirements are any other requirement than functional requirements. This are the requirements that specifies criteria that can be used to judge the operation of a system, rather than specific behaviours.
2. Non-functional requirements are in the form of "system shall be ", an overall property of the system as a whole or of a particular aspect and not a specific function. The system's overall properties commonly mark the difference between whether the development project has succeeded or failed.
3. Non-functional requirements - can be divided into two main categories:
Execution qualities , such as security and usability, which are observable at run time.
Evolution qualities such as testability, maintainability, extensibility and scalability, which are embodied in the static structure of the software system.
4. Non-functional requirements place restrictions on the product being developed, the development process, and specify external constraints that the product must meet.
5. The IEEE-Std 830 - 1993 lists 13 non-functional requirements to be included in a Software Requirements Document
Answer:
While functional requirements define what the system does or must not do, non-functional requirements specify how the system should do it. Non-functional requirements do not affect the basic functionality of the system (hence the name, non-functional requirements).
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