SEG3101-ch3-4 - Non-Functional Requirements - Qualities
[Pages:31]SEG3101 (Fall 2010)
Non-Functional Requirements
Gregor v. Bochmann, University of Ottawa
Based on Powerpoint slides by Gunter Mussbacher (2009) with material from:
Jo Atlee, Dan Berry (both University of Waterloo); R. Pressman; D. Damian; Amyot 2008, Som? 2008
Table of Contents
? Non-Functional Requirements and Software Quality
Attributes
? Software Quality ? Classifications of Non-Functional Requirements ? Quality Measures
? To measure is to know. If you can not measure it, you can not
improve it.1
[1] Lord Kelvin (1824 - 1907)
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SEG3101 (Fall 2010). Non-Functional requirements
3
SEG3101 (Fall 2010). Non-Functional requirements
Introduction to Requirements Specification
Software Quality
Software Quality (1)
Classifications of NFRs
Quality Measures
? Most definitions require compliance with requirements
? "Conformance to explicitly stated functional and performance
requirements, explicitly documented development standards,
and implicit characteristics that are expected of all professionally developed software."1
? Implication:
? We need to be able to explicitly quantify requirements and verify that any solution meets them
? We need measures
[1] Pressman, 1997
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SEG3101 (Fall 2010). Non-Functional requirements
Introduction to Requirements Specification
Software Quality
Software Quality (2)
? An interesting phenomenon:
Classifications of NFRs
Quality Measures
Measurable objectives are usually achieved!
? Therefore, unless you have unrealistic values, requirements
are usually met
? Important to know what measures exist! ? The chosen values, however, will have an impact on the
amount of work during development as well as the number of alternatives and architectural designs from which developers may choose to meet the requirements
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SEG3101 (Fall 2010). Non-Functional requirements
Introduction to Requirements Specification
Software Quality
Classifications of NFRs
Quality Measures
Types of Non-Functional Requirements (NFRs)
Non-fu nctional requir ement s
Pro du ct requir ements
Or gan izational requir ement s
Ex ternal requ irements
Ef ficiency requ ir ements
Reliab ility requir ements
Port ability requirement s
Interoperabilit y requirement s
Et hi cal requ irements
Usab ility requ ire m ent s
Del ive ry re qu irem ent s
Im pl em ent at io n requir ement s
Standard s requ irements
Leg is lat ive re qu irem ent s
P erfo rm ance requ ire m ent s
S p ace requ ir ements
Priv acy requ irements
Safety re qu irem ent s
Source: Gerald Kotonya and Ian Sommerville, Requirements Engineering ? Processes and Techniques, Wiley, 1998
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SEG3101 (Fall 2010). Non-Functional requirements
Introduction to Requirements Specification
Software Quality
Classifications of NFRs
Other Classification of NFRs (1)
Quality Measures
? Product-oriented attributes
? Performance : (a) response time, (b) throughput (number of operations performed per second)
? Usability: effort required to learn, use, provide input and interpret results of a program
? Efficiency: minimal use of resources (memory, processor, disk, network...)
? Reliability: of computations, precision ? Security ? Robustness: in the presence of faults, stress, invalid inputs... ? Adaptability: to other environments or problems ? Scalability: for large number of users or quantities of data ? Cost: total cost of ownership (TCO) for acquisition, installation, use,
disposal
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SEG3101 (Fall 2010). Non-Functional requirements
Introduction to Requirements Specification
Software Quality
Classifications of NFRs
Other Classification of NFRs (2)
Quality Measures
? Product family-oriented attributes
? Portability: does it work for several platforms ? Modifiability: addition of new functionalities ? Reusability: of components, code, designs, and even requirements in
other systems
? They are frequently demanded by developers to:
? Reduce development costs ? Increase revenues by creating several versions derived from a product or
by personalizing it
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SEG3101 (Fall 2010). Non-Functional requirements
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