XII. Non-Functional Requirements (or, Quality Factors)
Information Systems Analysis and Design
csc340
XII. Non-Functional Requirements (or, Quality Factors)
What are Non-Functional Reeqquuiirreemmeennttss ((NFRs)? Classification of NFRs Criteria and Factors
Portability, Reliability,, PPeerrffoorrmmaannccee Example NFR for an Automated Monneeyy MMaacchhiinnee
2003 John Mylopoulos
Non-Functional Requirements -- 1
Information Systems Analysis and Design
csc340
Non-Functional Requirements (NFRs)
Define global constraints on a software system, such as development costs, operational costs, performance, reliability, maintainability, portability, robustness etc.
Should not be confused with functional requirements, which impose requirements on the function of a system
Are generally stated informally, are often contradictory, difficult to enforce during development and to evaluate for the customer prior to delivery
How do we specify them?
2003 John Mylopoulos
Non-Functional Requirements -- 2
Page
Information Systems Analysis and Design
csc340
Types of NFRs
Interface requirements -- describe how the information system is to interface with its environment, users and other systems; include user interfaces and their qualities (e.g., "user-friendliness") Performance requirements -- describe performance constraints:
time/space bounds, such as workloads, response time, throughput and available storage space, e.g., "system must handle 1,000 transactions per second"); reliability involving the availability of components and integrity of information maintained and supplied to the system, e.g., "system must have less than 1hr downtime per three months" security, e.g., permissible information flows, who can do what; survivability, such as system will survive fire, natural catastrophes. Operating requirements -- include physical constraints (size, weight), personnel availability, skill level considerations, accessibility for maintenance, environmental conditions...
2003 John Mylopoulos
Non-Functional Requirements -- 3
Information Systems Analysis and Design
Types of NFRs
csc340
Lifecycle requirements -- can be classified under two subcategories:
Quality of the design, such as maintenability, enhanceability, portability; expected market or product lifespan,...(these don't affect initial system but may lead to increased maintenance costs or early obsolescence.)
Limits on development, other software lifecycle phases, such as development time limitations, resource availability, methodological standards etc.
Economic requirements -- immediate and/or long-term costs.
2003 John Mylopoulos
Page
Non-Functional Requirements -- 4
Information Systems Analysis and Design
csc340
(Different) Classification of NFRs
AAccqquuisisititioionnCCoonncceerrnn PPeerrfoforrmmaannccee
DDeessigignn AAddaappttaattioionn
UUsseer r CCoonncceerrnn RReessoouurrcceeuutitliilzizaatitoionn sseeccuurritiyty,,ccoonnfifdideennccee,,, ppeerrfoforrmmaanncceeuunnddeerrr aaddvveerrssitiyty,,eeaassee--ooff-f--uuussseee
CCoonnfoforrmmtotorereqqss??...... eeaassyytotorreeppaairir???......... vveerrifiifeieddppeerrfoforrmmaannccee??? EEaassyytotoeexxppaanndd?? .....u.uppggrraaddeefufunnccttitioioonnnooorrr ppeerrfoforrmmaannccee??? .....c.chhaannggee??.....i.ininntteteerrrffafaaccceee wwitihthaannooththeerrssyysstteteemmm??? .....p.poorrt?t?.....u.usseeiininnaaannnoootththheeerrr aapppplilcicaatitoionn??
QQuuaaliltityyFFaaccttoorrsss eefffifcicieiennccyy ininteteggrritiyty rerelilaiabbiliiltiyty ssuurvrvivivaabbiliiltiyty uussaabbiliiltiyty ccoorrrreecctntneessss mmaainintetennaabbiliiltiyty vveerirfiifaiabbiliiltiyty eexxppaannddaabbiliiltiyty flfelexxibibiliiltiyty ininteterrooppeerraabbiliiltiyty ppoorrtatabbiliiltiyty rereuussaabbiliiltiyty
2003 John Mylopoulos
Non-Functional Requirements -- 5
Information Systems Analysis and Design
csc340
Factors and Criteria
Factors are customer-related concerns, such as efficiency, integrity, reliability, correctness, survivability, usability,...
Criteria -- technical (development-oriented) concerns such as anomaly management, completeness, consistency, traceability, visibility,...
Each factor depends on a number of associated criteria, e.g., correctness depends on completeness, consistency, traceability,... verifiability depends on modularity, self-descriptiveness and simplicity
2003 John Mylopoulos
Page
Non-Functional Requirements -- 6
Information Systems Analysis and Design
csc340
(...A Year ago...) Canada - USA 5-2
2003 John Mylopoulos
Non-Functional Requirements -- 7
Information Systems Analysis and Design
Factors vs Criteria
csc340
factors -- customerrelated concerns criteria -- technical concerns
Reusability Portability Flexibility Verifiability Correctness Usability Survivability Reliability Integrity Efficiency
Factors
Criteria
Performance
Design Adaptation
Accuracy Performance
X
Anomaly Mngt
XX
Autonomy
X
Distributedness
X
Effectiveness storage X
Operability
X
System accessibility
X
Training
X
Completeness Design
X
Consistency
X
Traceability
X
Visibility
X
2003 John Mylopoulos
Non-Functional Requirements -- 8
Page
Information Systems Analysis and Design
Factors
csc340
Reusability Portability Flexibility Verifiability Correctness Usability Survivability Reliability Integrity Efficiency
Criteria
Performance
Applic. independAedanpcteation
Augmentability
Commonality
Doc. accessibility
Functional overlap
Functional scope
Generality
Independence
System clarity
System compatibility
Modularity
General
Self descriptiveness
Simplicity
X X
2003 John Mylopoulos
Design Adaptation
X
X
X XX
XX X
XXXX XXXX XX X
Non-Functional Requirements -- 9
Information Systems Analysis and Design
Quality Metrics
csc340
QQuuaaliltityy SSppeeeedd SSizizee EEaasseeooffUUssee RReelilaiabbiliiltityy RRoobbuussttnneessss PPoorrttaabbiliiltityy
MMeettrricic ttrraannssaaccttioionnss/s/seecc,,rreessppoonnsseettimimee ssccrreeeennrreeffrreesshhttimimee KKBByytteess nnuummbbeerrooffRRAAMMcchhipipss ttrraaininininggttimimee nnuummbbeerrooffhheelplpffrraammeess mmeeaann--ttimimee--ttoo--ffaailiulurree,,pprroobbaabbiliiltityyooffuunnaavvaailialabbiliiltityy rraatteeooffffaailiulurree,,aavvaailialabbiliiltityy ttimimeettoorreessttaarrttaafftteerrffaailiulurree ppeerrcceennttaaggeeooffeevveennttssccaauussininggffaailiulurree ppeerrcceennttaaggeeooffttaarrggeett--ddeeppeennddeennttssttaatteemmeennttss nnuummbbeerrooffttaarrggeettssyysstteemmss
2003 John Mylopoulos
Non-Functional Requirements -- 10
Page
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