ISO/IEC 25010:2011

Systems and software engineering - Systems and software Quality Requirements and Evaluation (SQuaRE) - System and software quality models

ISO/IEC 25010:2011 defines: A quality in use model composed of five characteristics (some of which are further subdivided into subcharacteristics) that relate to the outcome of interaction when a product is used in a particular context of use. This system model is applicable to the complete human-computer system, including both computer systems in use and software products in use. A product quality model composed of eight characteristics (which are further subdivided into subcharacteristics) that relate to static properties of software and dynamic properties of the computer system. The model is applicable to both computer systems and software products. The characteristics defined by both models are relevant to all software products and computer systems. The characteristics and subcharacteristics provide consistent terminology for specifying, measuring and evaluating system and software product quality. They also provide a set of quality characteristics against which stated quality requirements can be compared for completeness. Although the scope of the product quality model is intended to be software and computer systems, many of the characteristics are also relevant to wider systems and services. ISO/IEC 25012 contains a model for data quality that is complementary to this model. The scope of the models excludes purely functional properties, but it does include functional suitability. The scope of application of the quality models includes supporting specification and evaluation of software and software-intensive computer systems from different perspectives by those associated with their acquisition, requirements, development, use, evaluation, support, maintenance, quality assurance and control, and audit. The models can, for example, be used by developers, acquirers, quality assurance and control staff and independent evaluators, particularly those responsible for specifying and evaluating software product quality. Activities during product development that can benefit from the use of the quality models include: identifying software and system requirements; validating the comprehensiveness of a requirements definition; identifying software and system design objectives; identifying software and system testing objectives; identifying quality control criteria as part of quality assurance; identifying acceptance criteria for a software product and/or software-intensive computer system; establishing measures of quality characteristics in support of these activities.

Ingénierie des systèmes et du logiciel — Exigences de qualité et évaluation des systèmes et du logiciel (SQuaRE) — Modèles de qualité du système et du logiciel

General Information

• Status: Withdrawn
• Publication Date: 28-Feb-2011
• ICS: 35.080 - Software
• Technical Committee: ISO/IEC JTC 1/SC 7 - Software and systems engineering
• Drafting Committee: ISO/IEC JTC 1/SC 7/WG 6 - Software Product and System Quality
• Current Stage: 9599 - Withdrawal of International Standard
• Start Date: 04-Mar-2024
• Completion Date: 30-Oct-2025

Relations

• Revised: ISO/IEC 25002:2024 - Systems and software engineering - Systems and software Quality Requirements and Evaluation (SQuaRE) - Quality model overview and usage
• Effective Date: 23-Apr-2020
• Revised: ISO/IEC 25019:2023 - Systems and software engineering - Systems and software Quality Requirements and Evaluation (SQuaRE) - Quality-in-use model
• Effective Date: 23-Apr-2020
• Revised: ISO/IEC 25010:2023 - Systems and software engineering - Systems and software Quality Requirements and Evaluation (SQuaRE) - Product quality model
• Effective Date: 23-Apr-2020
• Revises: ISO/IEC 9126-1:2001 - Software engineering - Product quality - Part 1: Quality model
• Effective Date: 23-Oct-2010

Standards Content (Sample)

INTERNATIONAL ISO/IEC
STANDARD 25010
First edition
2011-03-01
Systems and software engineering —
Systems and software Quality
Requirements and Evaluation
(SQuaRE) — System and software quality
models
Ingénierie des systèmes et du logiciel — Exigences de qualité et
évaluation des systèmes et du logiciel (SQuaRE) — Modèles de qualité
du système et du logiciel
Reference number
©
ISO/IEC 2011
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ii © ISO/IEC 2011 – All rights reserved

Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Conformance .2
3 Quality model framework.2
3.1 Quality models.2
3.2 Quality in use model .3
3.3 Product quality model.3
3.4 Targets of the quality models .4
3.5 Using a quality model .5
3.6 Quality from different stakeholder perspectives .5
3.7 Relationship between the models .7
4 Terms and definitions .8
4.1 Quality in use model .8
4.2 Product quality model.10
4.3 General .16
4.4 Terms and definitions from ISO/IEC 25000.18
Annex A (informative) Comparison with the quality model in ISO/IEC 9126-1.21
Annex B (informative) Example of mapping to dependability.24
Annex C (informative) Using the quality model for measurement.26
Bibliography.33

© ISO/IEC 2011 – 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 document 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 25010 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 7, Software and systems engineering.
This first edition of ISO/IEC 25010 cancels and replaces ISO/IEC 9126-1:2001, which has been technically
revised.
ISO/IEC 25010 is a part of the SQuaRE series of International Standards, which consists of the following
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),
• Quality Evaluation Division (ISO/IEC 2504n),
• SQuaRE Extension Division (ISO/IEC 25050 – ISO/IEC 25099).
iv © ISO/IEC 2011 – All rights reserved

Introduction
Software products and software-intensive computer systems are increasingly used to perform a wide variety
of business and personal functions. Realization of goals and objectives for personal satisfaction, business
success and/or human safety relies on high-quality software and systems. High-quality software products and
software-intensive computer systems are essential to provide value, and avoid potential negative
consequences, for the stakeholders.
Software products and software-intensive computer systems have many stakeholders including those who
develop, acquire, use, or who are customers of businesses using software-intensive computer systems.
Comprehensive specification and evaluation of the quality of software and software-intensive computer
systems is a key factor in ensuring value to stakeholders. This can be achieved by defining the necessary and
desired quality characteristics associated with the stakeholders' goals and objectives for the system. This
includes quality characteristics related to the software system and data as well as the impact the system has
on its stakeholders. It is important that the quality characteristics are specified, measured, and evaluated
whenever possible using validated or widely accepted measures and measurement methods. The quality
models in this International Standard can be used to identify relevant quality characteristics that can be further
used to establish requirements, their criteria for satisfaction and the corresponding measures.
This International Standard is derived from ISO/IEC 9126:1991, Software engineering — Product quality,
which was developed to support these needs. It defined six quality characteristics and described a software
product evaluation process model.
ISO/IEC 9126:1991 was replaced by two related multipart standards: ISO/IEC 9126, Software engineering —
Product quality and ISO/IEC 14598, Software engineering — Product evaluation.
This International Standard revises ISO/IEC 9126-1:2001, and incorporates the same software quality
characteristics with some amendments.
• The scope of the quality models has been extended to include computer systems, and quality in use from
a system perspective.
• Context coverage has been added as a quality in use characteristic, with subcharacteristics context
completeness and flexibility.
• Security has been added as a characteristic, rather than a subcharacteristic of functionality, with
subcharacteristics confidentiality, integrity, non-repudiation, accountability and authenticity.
• Compatibility (including interoperability and co-existence) has been added as a characteristic.
• The following subcharacteristics have been added: functional completeness, capacity, user error
protection, accessibility, availability, modularity and reusability.
• The compliance subcharacteristics have been removed, as compliance with laws and regulations is part of
overall system requirements, rather than specifically part of quality.
• The internal and external quality models have been combined as the product quality model.
• When appropriate, generic definitions have been adopted, rather than using software-specific definitions.
• Several characteristics and subcharacteristics have been given more accurate names.
Full details of the changes are in Annex A.
This International Standard is intended to be used in conjunction with the other parts of the SQuaRE series of
International Standards (ISO/IEC 25000 to ISO/IEC 25099), and with ISO/IEC 14598 until superseded by the
ISO/IEC 2504n series of International Standards.
© ISO/IEC 2011 – All rights reserved v

Figure 1 (adapted from ISO/IEC 25000) illustrates the organization of the SQuaRE series representing
families of standards, further called divisions.

Figure 1 — Organization of SQuaRE series of International Standards
The divisions within the SQuaRE series are:
• ISO/IEC 2500n - Quality Management Division. The International Standards that form this division
define all common models, terms and definitions further referred to by all other International Standards
from the SQuaRE series. The division also provides requirements and guidance for a supporting function
that is responsible for the management of the requirements, specification and evaluation of software
product quality.
• ISO/IEC 2501n - Quality Model Division. The International Standards that form this division present
detailed quality models for computer systems and software products, quality in use, and data. Practical
guidance on the use of the quality models is also provided.
• ISO/IEC 2502n - Quality Measurement Division. The International Standards that form this division
include a software product quality measurement reference model, mathematical definitions of quality
measures, and practical guidance for their application. Examples are given of internal and external
measures for software quality, and measures for quality in use. Quality Measure Elements (QME) forming
foundations for these measures are defined and presented.
• ISO/IEC 2503n - Quality Requirements Division. The International Standards that form this division help
specify quality requirements, based on quality models and quality measures. These quality requirements
can be used in the process of quality requirements elicitation for a software product to be developed or as
input for an evaluation process.
• ISO/IEC 2504n - Quality Evaluation Division. The International Standards that form this division provide
requirements, recommendations and guidelines for software product evaluation, whether performed by
evaluators, acquirers or developers. The support for documenting a measure as an Evaluation Module is
also present.
vi © ISO/IEC 2011 – All rights reserved

• ISO/IEC 25050 – 25099 SQuaRE Extension Division. These International Standards currently include
requirements for quality of Commercial Off-The-Shelf software and Common Industry Formats for usability
reports.
The quality models in this International Standard can be used in conjunction with ISO/IEC 12207 and
ISO/IEC 15288, particularly the processes associated with requirements definition, verification and validation
with a specific focus on the specification and evaluation of quality requirements. ISO/IEC 25030 describes
how the quality models can be used for software quality requirements, and ISO/IEC 25040 describes how the
quality models can be used for the software quality evaluation process.
This International Standard can also be used in conjunction with ISO/IEC 15504 (which is concerned with
software process assessment) to provide:
• a framework for software product quality definition in the customer-supplier process;
• support for review, verification and validation, and a framework for quantitative quality evaluation, in the
support process;
• support for setting organizational quality goals in the management process.
This International Standard can be used in conjunction with ISO 9001 (which is concerned with quality
assurance processes) to provide:
• support for setting quality goals;
• support for design review, verification and validation.

© ISO/IEC 2011 – All rights reserved vii

INTERNATIONAL STANDARD ISO/IEC 25010:2011(E)

Systems and software engineering — Systems and software
Quality Requirements and Evaluation (SQuaRE) — System and
software quality models
1 Scope
This International Standard defines:
a) A quality in use model composed of five characteristics (some of which are further subdivided into
subcharacteristics) that relate to the outcome of interaction when a product is used in a particular context
of use. This system model is applicable to the complete human-computer system, including both
computer systems in use and software products in use.
b) A product quality model composed of eight characteristics (which are further subdivided into
subcharacteristics) that relate to static properties of software and dynamic properties of the computer
system. The model is applicable to both computer systems and software products.
The characteristics defined by both models are relevant to all software products and computer systems. The
characteristics and subcharacteristics provide consistent terminology for specifying, measuring and evaluating
system and software product quality. They also provide a set of quality characteristics against which stated
quality requirements can be compared for completeness.
NOTE Although the scope of the product quality model is intended to be software and computer systems, many of
the characteristics are also relevant to wider systems and services.
ISO/IEC 25012 contains a model for data quality that is complementary to this model.
The scope of the models excludes purely functional properties (see C.6), but it does include functional
suitability (see 4.2.1).
The scope of application of the quality models includes supporting specification and evaluation of software
and software-intensive computer systems from different perspectives by those associated with their
acquisition, requirements, development, use, evaluation, support, maintenance, quality assurance and control,
and audit. The models can, for example, be used by developers, acquirers, quality assurance and control staff
and independent evaluators, particularly those responsible for specifying and evaluating software product
quality. Activities during product development that can benefit from the use of the quality models include:
• identifying software and system requirements;
• validating the comprehensiveness of a requirements definition;
• identifying software and system design objectives;
• identifying software and system testing objectives;
• identifying quality control criteria as part of quality assurance;
• identifying acceptance criteria for a software product and/or software-intensive computer system;
• establishing measures of quality characteristics in support of these activities.
© ISO/IEC 2011 – All rights reserved 1

2 Conformance
Any quality requirement, quality specification, or evaluation of quality that conforms to this International
Standard shall either:
a) use the quality models defined in 4.1 and 4.2; or
b) tailor the quality model giving the rationale for any changes and provide a mapping between the tailored
model and the standard model.
3 Quality model framework
3.1 Quality models
The quality of a system is the degree to which the system satisfies the stated and implied needs of its various
stakeholders, and thus provides value. These stated and implied needs are represented in the SQuaRE series
of International Standards by quality models that categorize product quality into characteristics, which in some
cases are further subdivided into subcharacteristics. (Some subcharacteristics are divided into
sub-subcharacteristics.) This hierarchical decomposition provides a convenient breakdown of product quality.
However, the set of subcharacteristics associated with a characteristic have been selected to be
representative of typical concerns without necessarily being exhaustive.
The measurable quality-related properties of a system are called quality properties, with associated quality
measures. To arrive at measures of the quality characteristic or subcharacteristic, unless the characteristic or
subcharacteristic can be directly measured, it will be necessary to identify a collection of properties that
together cover the characteristic or subcharacteristic, obtain quality measures for each, and combine them
computationally to arrive at a derived quality measure corresponding to the quality characteristic or
subcharacteristic (see Annex C). Figure 2 shows the relationship between quality characteristics and
subcharacteristics, and quality properties.

Figure 2 — Structure used for the quality models
Currently there are three quality models in the SQuaRE series: the quality in use model and the product
quality model in this International Standard, and the data quality model in ISO/IEC 25012. The quality models
together serve as a framework to ensure that all characteristics of quality are considered. These models
provide a set of quality characteristics relevant to a wide range of stakeholders, such as: software developers,
system integrators, acquirers, owners, maintainers, contractors, quality assurance and control professionals,
and users.
2 © ISO/IEC 2011 – All rights reserved

The full set of quality characteristics across these models will not be relevant to every stakeholder.
Nonetheless, each category of stakeholder should be represented in reviewing and considering the relevance
of the quality characteristics in each model before finalizing the set of quality characteristics that will be used,
for example to establish product and system performance requirements or evaluation criteria.
3.2 Quality in use model
The quality in use model in 4.1 defines five characteristics related to outcomes of interaction with a system:
effectiveness, efficiency, satisfaction, freedom from risk, and context coverage (Figure 3 and Table 3). Each
characteristic can be assigned to different activities of stakeholders, for example, the interaction of an operator
or the maintenance of a developer.

Figure 3 — Quality in use model
The quality in use of a system characterizes the impact that the product (system or software product) has on
stakeholders. It is determined by the quality of the software, hardware and operating environment, and the
characteristics of the users, tasks and social environment. All these factors contribute to the quality in use of
the system.
Definitions and explanations of each quality characteristic for quality in use are given in 4.1.
Examples of quality in use measures are given in ISO/IEC TR 9126-4 (to be replaced by ISO/IEC 25024).
3.3 Product quality model
The product quality model in 4.2 categorizes system/software product quality properties into eight
characteristics: functional suitability, performance efficiency, compatibility, usability, reliability, security,
maintainability and portability. Each characteristic is composed of a set of related subcharacteristics (Figure 4
and Table 4).
© ISO/IEC 2011 – All rights reserved 3

Figure 4 — Product quality model
NOTE The need for compliance with standards or regulations can be identified as part of requirements for a system,
but these are outside the scope of the quality model.
The product quality model can be applied to just a software product, or to a computer system that includes
software, as most of the subcharacteristics are relevant to both software and systems.
Definitions and explanations of each quality characteristic for product quality are given in 4.2.
3.4 Targets of the quality models
Figure 5 illustrates the targets of the quality models and the related entities.
The product quality model focuses on the target computer system that includes the target software product,
and the quality in use model focuses on the whole human-computer system that includes the target computer
system and target software product. The target computer system also includes computer hardware, non-target
software products, non-target data, and target data, which is the subject of the data quality model (see C.8).
The target computer system is included in an information system that can also include one or more computer
systems and communication systems, such as a local area network and the Internet. The information system
is within a wider human-computer system (such as an enterprise system, embedded system or large-scale
control system) and can include users and the technical and physical usage environment. Where the
boundary of the system is judged to be, depends upon the scope of the requirements or evaluation, and upon
who the users are.
EXAMPLE If the users of an aircraft with a computer-based flight control system are taken to be the passengers,
then the system upon which they depend includes the flight crew, the airframe, and the hardware and software in the flight
control system, whereas if the flight crew are taken to be the users, then the system upon which they depend consists only
of the airframe and the flight control system.
Other stakeholders, such as software developers, system integrators, acquirers, owners, maintainers,
contractors, quality assurance and control professionals, will also be concerned with the quality.
4 © ISO/IEC 2011 – All rights reserved

NOTE This is conceptually the same as Figure 2 in ISO/IEC 25012 and Figure 5 in ISO/IEC 25030, but a different
version that focuses on quality models.
Figure 5 — Targets of quality models
3.5 Using a quality model
The product quality and quality in use models are useful for specifying requirements, establishing measures,
and performing quality evaluations (see Annex C). The defined quality characteristics can be used as a
checklist for ensuring a comprehensive treatment of quality requirements, thus providing a basis for estimating
the consequent effort and activities that will be needed during systems development. The characteristics in the
quality in use model and product quality model are intended to be used as a set when specifying or evaluating
computer system or software product quality.
It is not practically possible to specify or measure all subcharacteristics for all parts of a large computer
system or software product. Similarly it is not usually practical to specify or measure quality in use for all
possible user-task scenarios. The relative importance of quality characteristics will depend on the high-level
goals and objectives for the project. Therefore the model should be tailored before use as part of the
decomposition of requirements to identify those characteristics and subcharacteristics that are most important,
and resources allocated between the different types of measure depending on the stakeholder goals and
objectives for the product.
3.6 Quality from different stakeholder perspectives
The quality models provide a framework for collecting stakeholder needs. Stakeholders include the following
types of user:
1. Primary user: person who interacts with the system to achieve the primary goals.
2. Secondary users who provide support, for example
© ISO/IEC 2011 – All rights reserved 5

a) content provider, system manager/administrator, security manager;
b) maintainer, analyzer, porter, installer.
3. Indirect user: person who receives output, but does not interact with the system.
Table 1 — Examples of user needs for quality in use and product quality
User Primary user Secondary users Indirect user
needs Content provider Maintainer
Interacting Interacting Maintaining or porting Using output
Effectiveness How effective does the How effective does the How effective does the How effective does the
user need to be when content provider need person maintaining or person using output
using the system to to be when updating porting the system from the system need
perform their task? the system? need to be? to be?
Efficiency How efficient does the How efficient does the How efficient does the How efficient does the
user need to be when content provider need person maintaining or person using the
using the system to to be when updating porting the system output from the system
perform their task? the system? need to be? need to be?
Satisfaction How satisfied does the How satisfied does the How satisfied does the How satisfied does the
user need to be when content provider need person maintaining or person using the
using the system to to be when updating porting the system output from the system
perform their task? the system? need to be? need to be?
Freedom from risk How risk free does How risk free does How risk free does How risk free does
using the system to updating the content of making maintenance using the output from
perform their task the system need to changes to the system the system need to
need to be for the be? or porting the system be?
user? need to be?
Reliability How reliable does the How reliable does How reliable does How reliable does the
system need to be updating the system maintaining or porting output from the system
when the user uses it with new content need the system need to need to be?
to perform their task? to be? be?
Security How secure does the How secure does the How secure does the How secure does the
system need to be system need to be system need to be output from the system
when the user uses it after the content after maintenance need to be?
to perform their task? provider updates it? changes are made or
when it is ported?
Context coverage To what extent does To what extent does To what extent does To what extent does
the system need to be providing content need maintaining or porting using the output of the
effective, efficient, risk to be effective, the system need to be system need to be
free and satisfying in efficient, risk free and effective, efficient, risk effective, efficient, risk
all the intended and satisfying in all the free and satisfying in free and satisfying in
potential contexts of intended and potential all the intended and all the intended and
use? contexts of use? potential contexts of potential contexts of
use? use?
Learnability To what extent does To what extent does To what extent does To what extent does
learning to use the learning to provide learning to maintain or learning to use the
system need to be content need to be port the system need output from the system
effective, efficient, risk effective, efficient, risk to be effective, need to be effective,
free and satisfying? free and satisfying? efficient, risk free and efficient, risk free and
satisfying? satisfying?
Accessibility To what extent does To what extent does To what extent does To what extent does
the system need to be providing content for maintaining or porting using the output of the
effective, efficient, risk the system need to be the system need to be system need be
free and satisfying to effective, efficient, risk effective, efficient, risk effective, efficient, risk
use for people with free and satisfying for free and satisfying for free and satisfying for
disabilities? people with people with people with
disabilities? disabilities? disabilities?

6 © ISO/IEC 2011 – All rights reserved

Each of these types of user has needs for quality in use and product quality in particular contexts of use, as
illustrated for some examples of users and quality characteristics by the questions shown in Table 1.
NOTE The content provider will also have user needs for data quality.
The user needs in Table 1 provide examples of starting points for requirements, and can be used as a basis
for measuring the impact of the quality of the system on use and maintenance.
Prior to software development or acquisition, quality requirements should be defined from the perspective of
stakeholders. Analysis of the in use requirements will result in derived functional and quality requirements
needed for a product to achieve the in use requirements.
EXAMPLE Overall needs for system reliability can lead to specific requirements for software product maturity,
availability, fault tolerance and recoverability. Reliability can also have an impact on overall system effectiveness,
efficiency, freedom from risk and satisfaction.
3.7 Relationship between the models
The properties of the software product and computer system determine the product quality in particular
contexts of use (Table 2).
The functional suitability, performance efficiency, usability, reliability and security will have a significant
influence on the quality in use for primary users. Performance efficiency, reliability and security can also be
specific concerns of other stakeholders who specialize in these areas.
Compatibility, maintainability and portability will have a significant influence on quality in use for secondary
users who maintain the system.
Table 2 — Influence of the quality characteristics
Software product Computer Product quality Influence on Influence on Information
properties system characteristic quality in use for quality in use for system quality
properties primary users maintenance concerns of
tasks other
stakeholders
Æ
Functional
¬ ¬
suitability
Performance Æ
Æ
¬ ¬
efficiency
Compatibility
Æ
¬ ¬
Usability
¬ ¬ Æ
Reliability
Æ Æ
¬ ¬
Security
Æ Æ
¬ ¬
Maintainability
¬ ¬ Æ
Portability
Æ
¬ ¬
Key: ¬ These properties influence product quality.
Æ Product quality influences quality in use for these stakeholders.
© ISO/IEC 2011 – All rights reserved 7

4 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
NOTE Definitions of quality characteristics and subcharacteristics are given in 4.1 and 4.2, general definitions in 4.3
and the essential definitions from ISO/IEC 25000 are reproduced in 4.4.
4.1 Quality in use model
Quality in use is the degree to which a product or system can be used by specific users to meet their needs to
achieve specific goals with effectiveness, efficiency, freedom from risk and satisfaction in specific contexts of
use.
The properties of quality in use are categorized into five characteristics: effectiveness, efficiency, satisfaction,
freedom from risk and context coverage (Figure 3 and Table 3).
Table 3 — Quality in use characteristics and subcharacteristics
Effectiveness
Efficiency
Satisfaction
Usefulness
Trust
Pleasure
Comfort
Freedom from risk
Economic risk mitigation
Health and safety risk mitigation
Environmental risk mitigation
Context coverage
Context completeness
Flexibility
NOTE Usability (4.2.4) is defined as a subset of quality in use consisting of effectiveness, efficiency and satisfaction,
for consistency with its established meaning.
4.1.1
effectiveness
accuracy and completeness with which users achieve specified goals
[ISO 9241-11]
4.1.2
efficiency
resources expended in relation to the accuracy and completeness with which users achieve goals
[ISO 9241-11]
NOTE Relevant resources can include time to complete the task (human resources), materials, or the financial cost
of usage.
4.1.3
satisfaction
degree to which user needs are satisfied when a product or system is used in a specified context of use
NOTE 1 For a user who does not directly interact with the product or system, only purpose accomplishment and trust
are relevant.
8 © ISO/IEC 2011 – All rights reserved

NOTE 2 Satisfaction is the user’s response to interaction with the product or system, and includes attitudes towards
use of the product.
4.1.3.1
usefulness
degree to which a user is satisfied with their perceived achievement of pragmatic goals, including the results
of use and the consequences of use
4.1.3.2
trust
degree to which a user or other stakeholder has confidence that a product or system will behave as intended
4.1.3.3
pleasure
degree to which a user obtains pleasure from fulfilling their personal needs
NOTE Personal needs can include needs to acquire new knowledge and skills, to communicate personal identity and
to provoke pleasant memories.
4.1.3.4
comfort
degree to which the user is satisfied with physical comfort
4.1.4
freedom from risk
degree to which a product or system mitigates the potential risk to economic status, human life, health, or the
environment
NOTE Risk is a function of the probability of occurrence of a given threat and the potential adverse consequences of
that threat's occurrence.
4.1.4.1
economic risk mitigation
degree to which a product or system mitigates the potential risk to financial status, efficient operation,
commercial property, reputation or other resources in the intended contexts of use
4.1.4.2
health and safety risk mitigation
degree to which a product or system mitigates the potential risk to people in the intended contexts of use
4.1.4.3
environmental risk mitigation
degree to which a product or system mitigates the potential risk to property or the environment in the intended
contexts of use
4.1.5
context coverage
degree to which a product or system can be used with effectiveness, efficiency, freedom from risk and
satisfaction in both specified contexts of use and in contexts beyond those initially explicitly identified
NOTE Context of use is relevant to both quality in use and some product quality (sub)characteristics (where it is
referred to as “specified conditions”).
4.1.5.1
context completeness
degree to which a product or system can be used with effectiveness, efficiency, freedom from risk and
satisfaction in all the specified contexts of use
© ISO/IEC 2011 – All rights reserved 9

NOTE Context completeness can be specified or measured either as the degree to which a product can be used by
specified users to achieve specified goals with effectiveness, efficiency, freedom from risk and satisfaction in all the
intended contexts of use, or by the presence of product properties that support use in all the intended contexts of use.
EXAMPLE The extent to which software is usable using a small screen, with low network bandwidth, by a non-expert
user; and in a fault-tolerant mode (e.g. no network connectivity).
4.1.5.2
flexibility
degree to which a product or system can be used with effectiveness, efficiency, freedom from risk and
satisfaction in contexts beyond those initially specified in the requirements
NOTE 1 Flexibility can be achieved by adapting a product (see 4.2.8.1) for additional user groups, tasks and cultures.
NOTE 2 Flexibility enables products to take account of circumstances, opportunities and individual preferences that
had not been anticipated in advance.
NOTE 3 If a product is not designed for flexibility, it might not be safe to use the product in unintended contexts.
NOTE 4 Flexibility can be measured either as the extent to which a product can be used by additional types of users to
achieve additional types of goals with effectiveness, efficiency, freedom from risk and satisfaction in additional types of
contexts of use, or by a capability to be modified to support adaptation for new types of users, tasks and environments,
and suitability for individualization as defined in ISO 9241-110.
4.2 Product quality model
The product quality model categorizes product quality properties into eight characteristics (functional suitability,
reliability, performance efficiency, usability, security, compatibility, maintainability and portability). Each
characteristic is composed of a set of related subcharacteristics (Figure 4 and Table 4).
Reliability
(Sub)Characteristic  Maturity
Functional suitability  Availability
Functional completeness  Fault tolerance
Functional correctness  Recoverability
Functional appropriateness Security
Performance efficiency  Confidentiality
Time behaviour  Integrity
Resource utilization  Non-repudiation
Capacity  Accountability
Compatibility  Authenticity
Co-existence
Maintainability
Interoperability  Modularity
Usability  Reusability
Appropriateness recognizability  Analysability
Learnability  Modifiability
Operability  Testability
User error protection
Portability
User interface aesthetics  Adaptability
Accessibility  Installability
Replaceability
4.2.1
functional suitability
degree to which a product or system provides functions that meet stated and implied needs when used under
specified conditions
10 © ISO/IEC 2011 – All rights reserved

NOTE Functional suitability is only concerned with whether the functions meet stated and implied needs, not the
functional specification (see C.6).
4.2.1.1
functional completeness
degree to which the set of functions covers all the specified tasks and user objectives
4.2.1.2
functional correctness
degree to which a product or system provides the correct results with the needed degree of precision
4.2.1.3
functional appropriateness
degree to which the functions facilitate the accomplishment of specified tasks and objectives
EXAMPLE A user is only presented with the necessary steps to complete a task, excluding any unnecessary steps.
NOTE Functional appropriateness corresponds to suitability for the task in ISO 9241-110.
4.2.2
performance efficiency
performance relative to the amount of resources used under stated conditions
NOTE Resources can include other software products, the software and hardware configuration of the system, and
materials (e.g. print paper, storage media).
4.2.2.1
time behaviour
degree to which the response and processing times and throughput rates of a product or system, when
performing its functions, meet requirements
4.2.2.2
resource utilization
degree to which the amounts and types of resources used by a product or system, when performing its
functions, meet requirements
NOTE Human resources are included as part of efficiency (4.1.2).
4.2.2.3
capacity
degree to which the maximum limits of a product or system parameter meet requirements
NOTE Parameters can include the number of items that can be stored, the number of concurrent users, the
communication bandwidth, throughput of transactions, and size of database.
4.2.3
compatibility
degree to which a product, system or component can exchange information with other products, systems or
components, and/or perform its required functions, while sharing the same hardware or software environment
NOTE Adapted from ISO/IEC/IEEE 24765.
4.2.3.1
co-existence
degree to which a product can perform its required functions efficiently while sharing a common environment
and resources with other products, without detrimental impact on any other product
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4.2.3.2
interoperability
degree to which two or more systems, products or components can exchange information and use the
information that has been exchanged
NOTE Based on ISO/IEC/IEEE 24765.
4.2.4
usability
degree to which a product or system can be used by specified users to achieve specified goals with
effectiveness, efficiency and satisfaction in a specified context of use
NOTE 1 Adapted from ISO 9241-210.
NOTE 2 Usability can either be specified or measured as a product quality characteristic in terms of its
subcharacteristics, or specified or measured directly by measures that are a subset of quality in use.
4.2.4.1
appropriateness recognizability
degree to which users can recognize whether a product or system is appropriate for their needs
cf. functional appropriateness (4.2.1.3).
NOTE 1 Appropriateness recognizability will depend on the ability to recognize the appropriateness of the product or
system’s functions from initial impressions of the product or system and/or any associated documentation.
NOTE 2 The information provided by the product or system can include demonstrations, tutorials, documentation or, for
a web site, the information on the home page.
4.2.4.2
learnability
degree to which a product or system can be used by specified users to achieve specified goals of learning to
use the product or system with effectiveness, efficiency, freedom from risk and satisfaction in a specified
context of use
NOTE Can be specified or measured either as the extent to which a product or system can be used by specified
users to achieve specified goals of learning to use the product or system with effectiveness, efficiency, freedom from risk
and satisfaction in a specified context of use, or by product properties corresponding to suitability for learning as defined in
ISO 9241-110.
4.2.4.3
operability
degree to which a product or system has attributes that make it easy to operate and control
NOTE Operability corresponds to controllability, (operator) error tolerance and conformity with user expectations as
defined in ISO 9241-110.
4.2.4.4
user error protection
degree to which a system protects users against making errors
4.2.4.5
user interface aesthetics
degree to which a user interface enables pleasing and satisfying interaction for the user
NOTE This refers
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