Non-functional requirement

non-functional requirementsilitiesnon-functionalquality attributesnon-functional propertiesfunctional and non-functional constraintsnon-functional characteristicsnonfunctionalnonfunctional requirementperformance requirements
In systems engineering and requirements engineering, a non-functional requirement (NFR) is a requirement that specifies criteria that can be used to judge the operation of a system, rather than specific behaviors.wikipedia
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List of system quality attributes

ilitiesillitiesquality attributes
Non-functional requirements are often called "quality attributes" of a system.
Within systems engineering, quality attributes are realized non-functional requirements used to evaluate the performance of a system.

Functional requirement

functional requirementsfunctionalfunctional user requirements
They are contrasted with functional requirements that define specific behavior or functions.
Functional requirements are supported by non-functional requirements (also known as "quality requirements"), which impose constraints on the design or implementation (such as performance requirements, security, or reliability).

Requirement

requirementscustomer requirementcustomer needs
In systems engineering and requirements engineering, a non-functional requirement (NFR) is a requirement that specifies criteria that can be used to judge the operation of a system, rather than specific behaviors.

Performance engineering

performanceperformance engineerperformance monitoring
Performance engineering encompasses the techniques applied during a systems development life cycle to ensure the non-functional requirements for performance (such as throughput, latency, or memory usage) will be met.

Serviceability (computer)

serviceabilityfix or upgradeMaintainability
In software engineering and hardware engineering, serviceability (also known as supportability,) is one of the -ilities or aspects (from IBM's RAS(U) (Reliability, Availability, Serviceability, and Usability)).

Operability

inoperableoperable
Operability is considered one of the ilities and is closely related to reliability, supportability and maintainability.

FURPS

FURPS is an acronym representing a model for classifying software quality attributes (functional and non-functional requirements):

Architecturally significant requirements

The plan for implementing non-functional requirements is detailed in the system architecture, because they are usually architecturally significant requirements.
When talking about architecture, non-functional requirements or quality attributes is often used.

Usability

user-friendlyease of useuser friendly
Usability is a non-functional requirement.

Non-functional requirements framework

NFR (Non-Functional Requirements) is a framework on Goal Modelling.

Systems engineering

systems engineersystem engineeringsystems
In systems engineering and requirements engineering, a non-functional requirement (NFR) is a requirement that specifies criteria that can be used to judge the operation of a system, rather than specific behaviors.

Requirements engineering

requirementsrequirement engineeringrequirements engineer
In systems engineering and requirements engineering, a non-functional requirement (NFR) is a requirement that specifies criteria that can be used to judge the operation of a system, rather than specific behaviors.

Systems design

system designdesignsystems designer
The plan for implementing functional requirements is detailed in the system design.

Systems architecture

system architecturearchitecturesystems
The plan for implementing non-functional requirements is detailed in the system architecture, because they are usually architecturally significant requirements.

Function (mathematics)

functionfunctionsmathematical function
Functional requirements are usually in the form of "system shall do ", an individual action or part of the system, perhaps explicitly in the sense of a mathematical function, a black box description input, output, process and control functional model or IPO Model.

Black box

black-boxBlack box theoryBlack box analysis
Functional requirements are usually in the form of "system shall do ", an individual action or part of the system, perhaps explicitly in the sense of a mathematical function, a black box description input, output, process and control functional model or IPO Model.

Function model

functional modelfunctionalfunction modeling
Functional requirements are usually in the form of "system shall do ", an individual action or part of the system, perhaps explicitly in the sense of a mathematical function, a black box description input, output, process and control functional model or IPO Model.

IPO model

Input-Process-Output (IPO) modelinput–process–output model
Functional requirements are usually in the form of "system shall do ", an individual action or part of the system, perhaps explicitly in the sense of a mathematical function, a black box description input, output, process and control functional model or IPO Model.

Real-time computing

real-timereal timereal-time systems
If the number needs to be updated in real time, the system architects must ensure that the system is capable of displaying the record count within an acceptably short interval of the number of records changing.