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112:. In contrast, non-functional requirements are in the form of "system shall be <requirement>", 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.
119:" of a system. Other terms for non-functional requirements are "qualities", "quality goals", "quality of service requirements", "constraints", "non-behavioral requirements", or "technical requirements". Informally these are sometimes called the "
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A system may be required to present the user with a display of the number of records in a database. This is a functional requirement. How current this number needs to be, is a non-functional requirement. If the number needs to be updated in
76:, non-functional requirements are known as "architectural characteristics". Note that synchronous communication between software architectural components, entangles them and they must share the same architectural characteristics.
253:, 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.
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are usually in the form of "system shall do <requirement>", an individual action or part of the system, perhaps explicitly in the sense of a
123:", from attributes like stability and portability. Qualities—that is non-functional requirements—can be divided into two main categories:
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that specifies criteria that can be used to judge the operation of a system, rather than specific behaviours. They are contrasted with
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Chen, Lianping; Ali Babar, Muhammad; Nuseibeh, Bashar (2013). "Characterizing
Architecturally Significant Requirements".
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Execution qualities, such as safety, security and usability, which are observable during operation (at run time).
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Sufficient network bandwidth may be a non-functional requirement of a system. Other examples include:
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It is important to specify non-functional requirements in a specific and measurable way.
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Resource constraints (processor speed, memory, disk space, network bandwidth, etc.)
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Petter L. H. Eide (2005). "Quantification and
Traceability of Requirements".
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that define specific behavior or functions. The plan for implementing
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Broadly, functional requirements define what a system is supposed to
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and non-functional requirements define how a system is supposed to
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796:"Technical (Non-Functional) Requirements: An Agile Introduction"
894:"A Risk-Based, Value-Oriented Approach to Quality Requirements"
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410:(e.g. Operational System Monitoring, Measuring, and Management)
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Fundamentals of
Software Architecture: An Engineering Approach
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Flexibility (e.g. to deal with future changes in requirements)
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Emotional factors (like fun or absorbing or has "Wow! Factor")
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1004:"Non-Functional Requirements: Do User Stories Really Help?"
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510:(e.g. faults discovered, faults delivered, fault removal
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176:. Unsourced material may be challenged and removed.
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115:Non-functional requirements are often called the "
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416:Footprint reduction - reduce the exe files size
104:description input, output, process and control
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371:(resulting performance in relation to effort)
759:Stellman, Andrew; Greene, Jennifer (2005).
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439:issues or patent-infringement-avoidability
16:Type of requirement in systems engineering
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875:Zimmermann, Olaf; Stocker, Mirko (2021).
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236:Learn how and when to remove this message
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666:Architecturally Significant Requirements
613:(human factors) by target user community
67:architecturally significant requirements
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422:(e.g. ability to integrate components)
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661:Non-Functional Requirements framework
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365:(resource consumption for given load)
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174:adding citations to reliable sources
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821:Wiegers, Karl; Beatty, Joy (2013).
762:Applied Software Project Management
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1237:List of system quality attributes
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321:Cost, initial and Life-cycle cost
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383:Environmental protection
312:Configuration management
25:requirements engineering
481:performance engineering
343:Development environment
282:service level agreement
94:Functional requirements
41:functional requirements
1324:Management cybernetics
892:Glinz, Martin (2008).
656:Usability requirements
570:(horizontal, vertical)
298:, current and forecast
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651:Requirements analysis
98:mathematical function
74:software architecture
576:(cyber and physical)
170:improve this article
1314:Systems engineering
1220:Standards and lists
1044:. 19 November 2020.
1008:Methodsandtools.com
825:. Microsoft Press.
704:10.1109/MS.2012.174
455:Memory Optimization
447:mean time to repair
21:systems engineering
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854:. Addison-Wesley.
404:Failure management
117:quality attributes
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518:Readability
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477:Performance
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467:Open source
317:Conformance
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1192:Efficiency
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881:. LeanPub.
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601:Throughput
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536:Resilience
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363:Efficiency
358:Durability
338:Deployment
307:Compliance
196:newspapers
80:Definition
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1087:Qualities
1032:3 October
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102:black box
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