ISO/IEC 25020:2007

Software engineering - Software product Quality Requirements and Evaluation (SQuaRE) - Measurement reference model and guide

ISO/IEC 25020:2007 provides a measurement reference model and guide for measuring the quality characteristics defined in ISO/IEC 2501n, Quality Model Division. ISO/IEC 25020:2007 sets requirements for the selection and construction of quality measures. It also contains informative annexes addressing the following topics: criteria for selecting software quality measures and quality measure elements, demonstrating predictive validity and assessing measurement reliability, and an example format for documenting software quality measures. The Quality Measurement Division, of which ISO/IEC 25020 is a member, also offers examples of quality measures that can be used across the product development life cycle. These measures are defined in the other documents in the division and correspond to the quality characteristics in a software product quality model such as that described in ISO/IEC 25010. ISO/IEC 25020:2007 and the quality measures are designed to be used, in particular, with other standards in the SQuaRE series that address quality requirements (ISO/IEC 25030) and product quality evaluation (ISO/IEC 25040).

Ingénierie du logiciel — Exigences de qualité du produit logiciel et évaluation (SQuaRE) — Modèle de référence de mesure et guide

General Information

• Status: Withdrawn
• Publication Date: 17-May-2007
• Withdrawal Date: 17-May-2007
• ICS: 35.080 - Software
• Technical Committee: ISO/IEC JTC 1/SC 7 - Software and systems engineering
• Drafting Committee: ISO/IEC JTC 1/SC 7 - Software and systems engineering
• Current Stage: 9599 - Withdrawal of International Standard
• Start Date: 12-Jul-2019
• Completion Date: 30-Oct-2025

Relations

• Revised: ISO/IEC 25020:2019 - Systems and software engineering - Systems and software Quality Requirements and Evaluation (SQuaRE) - Quality measurement framework
• Effective Date: 06-Aug-2016

Standards Content (Sample)

INTERNATIONAL ISO/IEC
STANDARD 25020
First edition
2007-05-15
Software engineering — Software product
Quality Requirements and Evaluation
(SQuaRE) — Measurement reference
model and guide
Ingénierie du logiciel — Exigences de qualité du produit logiciel et
évaluation (SQuaRE) — Modèle de référence de mesure et guide

Reference number
©
ISO/IEC 2007
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©  ISO/IEC 2007
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
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ii © ISO/IEC 2007 – All rights reserved

Contents
Foreword . iv
Introduction.v
1 Scope .1
2 Conformance.1
3 Normative references .1
4 Terms and definitions.2
5 Symbols (and abbreviated terms).4
6 Software Product Quality Measurement .5
6.1 Software product quality measurement reference model (SPQM-RM) .5
6.2   Selecting software quality measures.5
6.3 Constructing software quality measures .6
Annex A (informative) Examples of criteria for selecting software quality measures and quality measure
elements.8
(informative)
Annex B Assessing measurement validity and reliability .10
(informative)
Annex C Example format for documenting software quality measures .12
Bibliography.15
© ISO/IEC 2007 – All rights reserved iii

Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission)
form the specialized system for worldwide standardization. National bodies that are members of ISO or IEC
participate in the development of International Standards through technical committees established by the
respective organization to deal with particular fields of technical activity. ISO and IEC technical committees
collaborate in fields of mutual interest. Other international organizations, governmental and non-governmental, in
liaison with ISO and IEC, also take part in the work. In the field of information technology, ISO and IEC have
established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. Draft International Standards
adopted by the joint technical committee are circulated to national bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the national bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this part of ISO/IEC 25020 may be the subject of
patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.
ISO/IEC FDIS 25020 is part of the SQuaRE series of standards and was prepared by Joint Technical Committee
ISO/IEC JTC 1, Information technology, Subcommittee SC 7, Software and systems engineering.
SQuaRE series of standards consists of the following divisions under the general title Software engineering,
Software product Quality Requirements and Evaluation (SQuaRE):
Quality Management Division (ISO/IEC 2500n),
—
Quality Model Division (ISO/IEC 2501n),
—
— Quality Measurement Division (ISO/IEC 2502n),
Quality Requirements Division (ISO/IEC 2503n), and
—
Quality Evaluation Division (ISO/IEC 2504n).
—
iv © ISO/IEC 2007 – All rights reserved

Introduction
The general goal of creating the SQuaRE series of International Standards is to move to a logically organized,
enriched and unified series covering three complementary processes: requirements specification, measurement
and evaluation. The purpose of the SQuaRE series of International Standards is to assist those developing and
acquiring software products with the specification and evaluation of quality requirements. It establishes criteria for
the specification of software product quality requirements and their evaluation. It includes a two-part quality model
for aligning customer definitions of quality with characteristics of the software product. In addition, the series
defines measures of software product quality characteristics that can be used by developers, acquirers and
evaluators.
It has to be stressed that the SQuaRE series of International Standards is dedicated to software product quality
only. The Quality Management Division of the SQuaRE series deals with software products, and is separate and
distinct from the "Quality Management" of processes which is defined in the ISO 9000 family of International
Standards.
The major benefits of the SQuaRE series over its predecessor standards include:
— the coordination of guidance on software product quality measurement and evaluation,

— guidance for the specification of software product quality requirements, and

— harmonization with ISO/IEC 15939 in the form of Quality Measurement Reference model presented in this
International Standard.
The major differences between the SQuaRE series of International Standards and its predecessors, ISO/IEC 9126
and ISO/IEC 14598, are the:
— introduction of the new general reference model,

— introduction of dedicated and detailed guides for each division,

— introduction of Quality Measure Elements within the Quality Measurement Division,

— introduction of the Quality Requirements Division,

— incorporation and revision of the evaluation processes,

— introduction of guidance for practical use in the form of examples, and

— co-ordination and harmonization of content with ISO/IEC 15939.

SQuaRE consists of the following five divisions:

— Quality Management Division (ISO/IEC 2500n),

— Quality Model Division (ISO/IEC 2501n),

— Quality Measurement Division (ISO/IEC 2502n),

— Quality Requirements Division (ISO/IEC 2503n), and

— Quality Evaluation Division (ISO/IEC 2504n).

SQuaRE provides:
— terms and definitions,
© ISO/IEC 2007 – All rights reserved v

— reference models,
— a general guide,
— individual division guides, and

— standards for requirements specification, measurement and evaluation purposes.

SQuaRE includes International Standards and technical reports for a quality model and measures, as well as on
quality requirements and evaluation. SQuaRE replaces current ISO/IEC 9126 series and ISO/IEC 14598 series.

This International Standard is intended to be used together with ISO/IEC 25010. It is strongly recommended that
users refer to ISO/IEC 2500n, ISO/IEC 2501n, ISO/IEC 2503n, and ISO/IEC 2504n division of International
Standards prior to using this International Standard and the associated measurement technical reports, particularly
if the user is not familiar with the use of software measures for requirements specification and product evaluation.
These International Standards discuss the planning and use of the software quality measures defined in the
ISO/IEC 2502n series on software product quality measurement.

ISO/IEC 25010 will provide a model and defines terms for software product quality characteristics and how these
characteristics are decomposed into subcharacteristics. It does not describe how any of these subcharacteristics
could be measured. The Quality Measurement Division provides information and guidance about how to measure
the characteristics and subcharacteristics of a quality model. This International Standard provides a reference
model and guide for measuring the quality characteristics defined in ISO/IEC 2501n Quality Model Division
(Figure 1). The associated standards and technical reports within the Quality Measurement Division describe
measures of quality throughout the product life cycle.

ISO/IEC 25021 offers quality measure elements that can be used to construct software quality measures. Quality
measure elements are the base and derived measures used to create measures of software product quality
characteristics. Quality measure elements may measure a static representation of the software, the behaviour of
the software, or the effects of the software when it is used.

ISO/IEC 25022, ISO/IEC 25023 and ISO/IEC 25024 will describe measures for the characteristics in the quality
model. Internal measures characterize software product quality based upon static representations of the software,
external measures characterize software product quality based upon the behaviour of the computer-based system
including the software, and quality in use measures characterize software product quality based upon the effects of
using the software in a specific context of use.

The measures in these technical reports should not be construed as an exhaustive or required set. Figure 2
depicts the relationship between this International Standard and the technical reports in the Quality Measurement
Division. Developers, evaluators, quality managers, acquirers, suppliers, maintainers and other users of software
may select measures from these technical reports for the measurement of quality characteristics of interest. In
practice this may be with respect to defining requirements, evaluating software products, quality management and
other purposes. Users may also modify the measures or use measures which are not included in those technical
reports.
vi © ISO/IEC 2007 – All rights reserved

Quality Model Division
2501n
Quality
Quality
Quality
Evaluation
Requirements
Management Division
Division
Division
2500n
2504n
2503n
Quality
Measurement Division
2502n
Figure 1 — Organization of the SQuaRE series of International Standards

MeasMeasururemeemennt rt reeferfereencnce e
momoddeell a and nd gguuiiddee
2502502323 2502502424
MMeaseasururememeent ont off MeasMeasururemeemennt ot off
MMeaseasururememeenntt o off q quuaallitityy
iinntteerrnnal qal quualalityity exexterternnalal q quualialittyy
inin u ussee
QuaQuallityity me measasurure e
elelememeentsnts
Figure 2 — Structure of the Quality Measurement division
© ISO/IEC 2007 – All rights reserved vii

INTERNATIONAL STANDARD ISO/IEC 25020:2007(E)

Software engineering — Software product Quality
Requirements and Evaluation (SQuaRE) — Measurement
reference model and guide
1 Scope
The scope of this International Standard is the selection and construction of software product quality measures,
with respect to their use in conjunction with the other SQuaRE series documents.
This International Standard also contains the following informative annexes (A through C) and Bibliography:
— Criteria for selecting software quality measures and quality measure elements
— Demonstrating predictive validity and assessing measurement reliability
— Example format for documenting software quality measures
— Bibliography
The SQuaRE series of International Standards is intended for, but not limited to, developers, acquirers and
independent evaluators of software, particularly those responsible for defining software product quality
requirements and for software product evaluation. It is recommended that users of SQuaRE use this International
Standard as a guide to execute their software product quality measurement tasks.
2 Conformance
Any software product quality measurement that conforms to this International Standard shall fulfil the requirements
of Clause 6.
3 Normative references
The following referenced documents are indispensable for the application of this document. For dated references,
only the edition cited applies. For undated references, the latest edition of the referenced document (including any
amendments) applies.
ISO/IEC 25000, Software Engineering — Software product Quality Requirements and Evaluation (SQuaRE) —
Guide to SQuaRE
ISO/IEC 15939:2002, Software engineering — Software measurement process

© ISO/IEC 2007 – All rights reserved 1

4 Terms and definitions
For the purposes of this standard, the terms and definitions given in ISO/IEC 25000 and ISO/IEC 15939 apply.
The following definitions are replicated here for the convenience of the user of this Internationl Standard.
Unattributed references are from ISO/IEC 25000.
4.1
attribute
inherent property or characteristic of an entity that can be distinguished quantitatively or qualitatively by human or
automated means
[ISO/IEC 15939:2002]
NOTE  ISO 9000 distinguishes two types of attributes: a permanent characteristic existing inherently in something; and an
assigned characteristic of a product, process or system (e.g. the price of a product, the owner of a product). The assigned
characteristic is not an inherent quality characteristic of that product, process or system.
4.2
base measure
measure defined in terms of an attribute and the method for quantifying it
NOTE  A base measure is functionally independent of other measures.
[ISO/IEC 15939: 2002, based on the definition in International Vocabulary of Basic and General Terms in
Metrology, 1993]
4.3
derived measure
measure that is defined as a function of two or more values of base measures
[ISO/IEC 15939:2002, based on the definition in International Vocabulary of Basic and General Terms in Metrology,
1993]
NOTE A transformation of a base measure using a mathematical function can also be considered as a derived measure.
4.4
external software quality
capability of a software product to enable the behaviour of a system to satisfy stated and implied needs when the
system is used under specified conditions
NOTE Attributes of the behaviour can be verified and/or validated by executing the software product during testing and
operation.
EXAMPLE The number of failures found during testing is an external software quality measure related to the number of faults
present in the program. The two measures are not necessarily identical since testing may not find all faults, and a fault may
give rise to apparently different failures in different circumstances.
4.5
indicator
measure that provides an estimate or evaluation of specified attributes derived from a model with respect to defined
information needs
[ISO/IEC 15939:2002]
NOTE In ISO/IEC 14598 this definition was, "a measure that can be used to estimate or predict another measure."
2 © ISO/IEC 2007 – All rights reserved

4.6
information need
insight necessary to manage objectives, goals, risks and problems
[ISO/IEC 15939:2002]
4.7
internal software quality
capability of a set of static attributes of a software product to satisfy stated and implied needs when the software
product is used under specified conditions
NOTE 1 Static attributes include those that relate to the software architecture, structure and its components.
NOTE 2 Static attributes can be verified by review, inspection and/or automated tools.
EXAMPLE The number of lines of code, complexity measures and the number of faults found in a walk through are all internal
software quality measures made on the product itself.
4.8
measure, noun
variable to which a value is assigned as the result of measurement
NOTE The term “measures” is used to refer collectively to base measures, derived measures and indicators.
[ISO/IEC 15939:2002]
4.9
measure, verb
make a measurement
[ISO/IEC 14598-1:1999]
4.10
measurement
set of operations having the object of determining a value of a measure
[ISO/IEC 15939:2002, based on the definition in International Vocabulary of Basic and General Terms in Metrology,
1993]
NOTE Measurement can include assigning a qualitative category such as the language of a source program
(ADA, C, COBOL, etc.).
4.11
measurement function
algorithm or calculation performed to combine two or more base measures
[ISO/IEC 15939:2002]
© ISO/IEC 2007 – All rights reserved 3

4.12
measurement method
logical sequence of operations, described generically, used in quantifying an attribute with respect to a specified
scale
[ISO/IEC 15939:2002, based on the definition in International Vocabulary of Basic and General Terms in Metrology,
1993]
4.13
quality in use (measure)
extent to which a product used by specific users meets their needs to achieve specific goals with
effectiveness, productivity, safety and satisfaction in specific contexts of use
4.14
quality measure element
measure, which is either a base measure or a derived measure, that is used for constructing software quality
measures
NOTE  The software quality characteristic or subcharacteristic of the entity is derived afterwards by calculating a software
quality measure.
5 Symbols (and abbreviated terms)
The following symbols and abbreviations are used in this International Standard.
SPQM-RM – Software Product Quality Measurement Reference Model
4 © ISO/IEC 2007 – All rights reserved

6 Software Product Quality Measurement
6.1 Software product quality measurement reference model
The software product quality measurement reference model (SPQM-RM) describes the relationship between a
quality model, its associated quality characteristics (and subcharacteristics), and software product attributes with
the corresponding software quality measures, measurement functions, quality measure elements, and
measurement methods. These relationships constitute the reference model for software product quality
measurement. Figures 3 and 4 depict the relationships between the quality model and the construction of quality
measures from quality measure elements. The measurement information model presented in Annex A of ISO/IEC
15939 describes the relationship between software product attributes and the measurement methods used to
produce base and derived measures which, in turn, may be used as quality measure elements. The left side of
Figure 3 shows that software product quality is composed of quality characteristics which in turn may be composed
of subcharacteristics. The decomposition of software product quality may go through several levels although the
nominal model contained in ISO/IEC 25010 only contains two levels. The right side of Figure 3 shows that software
quality measures are used to indicate the quality characteristics and subcharacteristics of interest. Refer to ISO/IEC
25030 for guidance on selecting quality characteristics and subcharacteristics of interest in conjunction with the
specification of quality requirements and ISO/IEC 25040 for guidance on using software quality measures for
software product evaluation.
Figure 3 also shows that software quality measures are constructed by applying quality measure elements to a
measurement function. In the special case where the quality measure element also serves as a software
quality measure, the measurement function applied would be the identity function.
Quality measure elements may be either base or derived measures. Quality measure elements are constructed in
accordance with the guidance provided in ISO/IEC 15939.

SoftSoftwwaarere Pr Prododuucctt

QuQuaallitityy
composecomposedd of of
Software
inindicatdicatee
QQuualalitityy M Meeaassurureses
QuQuaallitityy
genergeneraatetess
ChChararacacteristeristticsics
MeMeasasurureemmeenntt
composecomposedd of of
FunctFunctiionon
indindicaticatee
arare ape appplieliedd ttoo
QuQuaallitityy
QuaQuallitityy M Measeasuurree
SuSubb-C-Chharaaracctteerriissttiiccss
ElemenElementsts
Figure 3 – Software Product Quality Measurement Reference Model (SPQM-RM)

6.2   Selecting software quality measures
Software quality measures are selected to satisfy the needs of developers, acquirers, managers, and others for
information. In the context of the SQuaRE series, information needs may be defined by quality requirements
specifications and product quality evaluations.
6.2.1 Criteria for selecting software quality measures and quality measure elements to fulfil those
information needs shall be documented.
© ISO/IEC 2007 – All rights reserved 5

At a minimum, the criteria shall be listed along with the assessment of the selected measures against the stated
criteria. Annex A provides exampl
...