ISO/IEC 24756:2009

INTERNATIONAL ISO/IEC
STANDARD 24756
First edition
2009-04-01

Information technology — Framework
for specifying a common access profile
(CAP) of needs and capabilities of users,
systems, and their environments
Technologies de l'information — Cadre de définition d'un profil d'accès
commun (CAP) des besoins et capacités des utilisateurs, des systèmes
et de leurs environnements




Reference number
ISO/IEC 24756:2009(E)
©
ISO/IEC 2009

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ISO/IEC 24756:2009(E)
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ISO/IEC 24756:2009(E)
Contents Page
Foreword. v
Introduction . vi
1 Scope . 1
2 Conformance. 1
3 Normative references . 1
4 Terms and definitions. 1
5 A model of accessibility. 2
6 A format for identifying access potential. 5
6.1 Introduction to the Common Access Profile . 5
6.2 Common Access Profile . 6
6.3 Describing Overall CAPs . 7
6.4 Describing Interacting Components. 8
6.5 Describing IC Component Features. 8
6.6 Modality-specific information. 10
6.7 Capability-specific information . 12
6.8 Processing-specific information. 16
6.9 Expanding the CAP. 18
7 Operations on CAPs. 19
7.1 CAP operators. 19
7.2 Unary operations . 19
7.2.1 Required (SHALL). 19
7.2.2 Optional (MAY) . 19
7.2.3 Exclusion (NOT). 20
7.3 Binary operations . 20
7.3.1 Included (AND) . 20
7.3.2 Substitutable (OR) . 21
7.3.3 Mutually exclusive (XOR). 21
8 Applying the CAP. 22
8.1 Introduction to applying the CAP. 22
8.2 Applying the CAP to identifying handicaps. 22
8.3 Applying the CAP to selecting ATs. 23
8.4 Applying the CAP to managing ATs . 23
8.4.1 Developing a base configuration . 23
8.4.2 Developing alternate configurations . 24
8.4.3 Reconfiguring current configurations. 24
Annex A (informative) Example Common Access Profile. 25
A.1 Introduction . 25
A.2 Users . 25
A.2.1 Introduction to User CAPs. 25
A.2.2 Description of Johann. 26
A.2.3 A note on hearing . 27
A.2.4 Johann’s CAP. 28
A.3 Systems . 35
A.3.1 Introduction to System CAPs . 35
A.3.2 The CAP approach to Systems . 36
A.3.3 Description of Example System . 36
A.3.4 Example system’s CAP . 37
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ISO/IEC 24756:2009(E)
A.4 For more information. 50
Annex B (informative) Developers of this International Standard. 51
Bibliography . 52

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ISO/IEC 24756:2009(E)
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 24756 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 35, User interfaces.
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ISO/IEC 24756:2009(E)
Introduction
Users of various systems in various environments can experience temporary or permanent accessibility
difficulties. Potential users of systems need to evaluate whether the systems will be accessible to them in the
intended environments in which they will be used. Where accessibility can be insufficient, either due to
environmental barriers or poor design, these users can wish to resort to assistive technologies (ATs) to
provide the required level of accessibility. Currently, there is no common framework for describing accessibility
needs or abilities. This requires each potential user to develop their own evaluation method, and then to
investigate and evaluate various systems and ATs using this method. However, due to the lack of an existing
method, there might also be a lack of suitable information on the abilities of different systems and ATs, leading
to inefficiency, confusion, frustration and a general lack of satisfaction by the user.
A variety of difficulties can be encountered when trying to identify suitable ATs to improve accessibility.
Accessibility issues being encountered by potential users can inhibit them from obtaining the required
information to identify possible ATs that could help improve their accessibility. Lack of experience with ATs
can also affect information technology support staff who attempt to assist these potential users.
The need for accessibility extends to all systems that a proposed user can access. The ability for information
gathered regarding accessibility issues and solutions for individual users to be portable across systems and
environments is essential. This International Standard introduces a model of accessibility as a basis for
understanding access issues with the interactions between users and systems in various environments.
Accessibility is multi-dimensional; existing at multiple levels. The model shows that users and systems must
share capabilities of communicating. This International Standard provides a framework to specify a profile of
common access capabilities (the CAP) of interactive systems, users, and their environment that are necessary
for accessibility to be possible.
The CAP is specified in a top-down manner that provides extensibility to be able to include capabilities at
increasingly detailed levels.

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INTERNATIONAL STANDARD ISO/IEC 24756:2009(E)

Information technology — Framework for specifying a common
access profile (CAP) of needs and capabilities of users,
systems, and their environments
1 Scope
This International Standard defines a framework for specifying a common access profile (CAP) of needs and
capabilities of users, computing systems, and their environments, including access that is supported by
assistive technologies. It provides a basis for identifying and dealing with accessibility issues in a standardised
manner across multiple platforms. It can be used to evaluate the accessibility of existing systems in particular
environments for particular users.
2 Conformance
Specifications for systems and/or system components, including assistive technologies, conform to
ISO/IEC 24756 if they conform to Clauses 6 and 7 of this International Standard.
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 639-3, Codes for the representation of names of languages — Part 3: Alpha-3 code for comprehensive
coverage of languages
ISO 15924, Information and documentation — Codes for the representation of names of scripts
ISO 80000 (all parts), Quantities and units
4 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
4.1
accessibility
usability of a product, service, environment or facility by people with the widest range of capabilities
NOTE 1 The concept of accessibility addresses the full range of user capabilities and is not limited to users who are
formally recognised as having a disability.
NOTE 2 The usability-orientated concept of accessibility aims to achieve levels of effectiveness, efficiency and
satisfaction that are as high as possible considering the specified context of use, while paying particular attention to the full
range of capabilities within the user population.
[ISO 9241-171:2008, definition 3.2]
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ISO/IEC 24756:2009(E)
4.2
usability
extent to which a product can be used by specified users to achieve specified goals with effectiveness,
efficiency, and satisfaction in a specified context of use
[ISO 9241-11:1998, definition 3.1]
4.3
assistive technology
AT
hardware or software that is added to or incorporated within a system that increases accessibility for an
individual
EXAMPLE Braille displays, screen readers, screen magnification software and eye tracking devices are assistive
technologies.
[ISO 9241-171:2008, definition 3.5]
4.4
context of use
users, tasks, equipment (hardware, software, and materials), and the physical and social environments in
which a product is used
[ISO 9241-11:1998, definition 3.5]
4.5
handicap
anything that might interfere with the accessibility of interactions between users and systems
5 A model of accessibility
Accessibility involves usable interaction between a user and a system. This interaction takes place within a
context of use that includes the system, the user, the user’s tasks, and the environment. Figure 1 illustrates
the environment in which this interaction takes place. Handicaps are anything that might interfere with the
accessibility of interactions between users and systems. A handicap can have one or many sources among
the system, user, interaction, and/or environment. This model is “blame-free,” since resolving any handicap to
the interaction is more important than attributing blame to the source of the handicap.
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ISO/IEC 24756:2009(E)
CONTEXT
ENVIRONMENT
INTERACTION
USER SYSTEM
HANDICAP
INTERACTION

Figure 1 — A model of the User-System interaction
The figure uses a pipe metaphor to illustrate the flow of interactions between the user and the system and a
valve metaphor to illustrate various levels of handicaps to the interaction(s). The shaded flow between user
and system illustrates the possibility of multiple communications occurring in either direction. A fully open
valve represents the absence of a handicap to the interaction. A fully closed valve represents an interaction
being fully handicapped. Any other setting of the valve represents an interaction being partially handicapped.
While universal design features can reduce handicaps to interactions, it cannot eliminate all handicaps of the
interactions in all situations. An assistive technology (AT) is a means of reducing such handicaps. While a
consumer of an AT might not have a disability, there can be some component of the interaction that is
“handicapping” them. For example, one could attend a lecture where the speaker uses a language unknown
to the listener. Since most people know at least one language, the listener might eventually come to know the
language the presentation is given in, but the interaction between speaker and listener is currently
handicapped by one not knowing the language used by the other at the present time. The listener’s task of
following the details of the presentation would not be possible without the use of a translator to bridge the
interaction between the listener and the speaker. In this sense, the translator would be an AT.
Computer related ATs can be realised through: alternative input devices (e.g., trackball, left-handed mouse,
sip/puff systems), alternative output devices (e.g., voice, Braille display), accessible software (e.g., screen
magnification software), and “universal design” (i.e., barrier-free design). Since the interaction is what is being
handicapped, an accessible computing experience is realised by a reduction of this handicap.
ATs can be modelled as a means of opening the valve between systems and users, as shown in Figure 2.
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ISO/IEC 24756:2009(E)
CONTEXT
CONTEXT CONTEXT
ASSISTIVE
USER SYSTEM
TECHNOLOGY

Figure 2 — Assistive Technology in the User-System interaction
Accessibility relies on users and systems using compatible interfaces for interaction. The inclusion of an AT
allows translation between two incompatible interfaces as illustrated in Figure 3. To evaluate current and
proposed future accessibility, there is a need for a standard method to describe both user-system accessibility
and user-AT-system accessibility across all users and systems.
SYSTEM
USER AT

Figure 3 — Interfacing between components
The goal of accessibility is to make systems accessible to users. However, different situations call for different
packaging(s) of systems. Where the user’s goal is to interact with a particular application package, the user
can choose the operating system, computer, peripherals, and other ATs that make the application the most
accessible. ATs might be required for accessibility purposes where the user’s goal is to interact with an
application package that is part of an existing hardware/software system.
The model presented in Figure 3 holds in all situations regardless of the different possible locations of system
boundaries. In this model, ATs can be considered anything that is added to the basic system to make it
accessible to users. There is a very wide range of objects that can act as ATs, including: special purpose
assistive technologies, universal remote consoles, intelligent agents, and even components that are
specifically chosen to meet the accessibility needs of a particular user. Multiple ATs can be used in sequence
and/or in parallel to support access.
Figure 4 illustrates the paths between the User and their ultimate goal, the application (A1, A2, A3) the user
wants to use. Multiple communications can occur in either direction along the connecting lines between
components. The applications being used must be accessible to the user. To this end, software-based
Assistive Technology (SAT), software which may be part of the operating system or software that is added to
the system to increase accessibility for an individual user, might be needed. Examples of SATs include add-on
or built-in screen readers.
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Processing
Interface
User – AT
Interface
Processing
System – AT
Interface
Interface
Processing

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ISO/IEC 24756:2009(E)

Figure 4 — Components of accessibility
Although not traditionally considered assistive technology, each of the layers (Operating System, Hardware,
Peripherals, Assistive Technology, and Environment) between the user and the application has the same
effect as an AT in either increasing or decreasing access. The choice of operating system (OS1, OS2) to use
with the application can limit or increase the user’s access to the application. It can limit access where it does
not support certain forms of interaction between the user and the application. It might increase access where it
supports transformations of interactions between the user and the application from one form of interaction to
another. The computer (C) with which the operating system interacts might limit the user’s experience still
further. Users are also limited by the capabilities of peripherals (P1, P2, P3) available with the computer.
The user might perceive the combination of application, operating system, computer, and peripherals as a
single system, as is indicated by a dotted box in the figure. When considering accessibility, these components
can be modelled separately or as a single system.
Assistive Technologies (AT1, AT2) can be used to transform interactions of peripherals to make them more
accessible. Environmental conditions (E) can further degrade the accessibility of certain interactions.
To the user, the total experience with all of these components might be perceived as a total system. It is the
total system that needs to be specified to evaluate accessibility for the user.
6 A format for identifying access potential
6.1 Introduction to the Common Access Profile
Communications are transmitted (by systems, users, or ATs through channels and environments) to their
intended receptors (systems, users, or ATs). This involves flows of information from the system to the user
and from the user to the system. The characteristics of these flows are not necessarily the same (e.g., the
system might provide spoken output which the user can hear however, if the user has a speech disability, they
might choose to use a keyboard to input information to the system). Access exists when the receptor is able to
receive and understand the message as transmitted. In this International Standard, systems, users, ATs,
environments, and channels will be considered Interacting Components (ICs). Individual communications can
be modelled in terms of the receptors, channels, and transmitters used to accomplish the communication.
Interaction involves many sets of communications going in either direction between the ICs in the interaction.
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ISO/IEC 24756:2009(E)
An access framework modelling all of the sets of transmitters, channels, and receptors involved in the set of
possible interactions between a particular user and a particular system can be used to evaluate the
accessibility of a system in a given environment to a particular user.
This access framework involves multiple sets of:
{ Interactions each of which is composed of one or more sets of { receptor, channel, transmitter } }
Rather than deal with each interaction, it is possible to model the set of potential interactions based on an
understanding of the compatibility of transmitters, receptors, and channel characteristics of the ICs.
6.2 Common Access Profile
An overall Common Access Profile (CAP ) is composed of the CAP of each different Interacting Component
O IC
(IC), including those of: users (CAP ), systems (CAP ), assistive technologies (CAP ), and
USE SYS AT
environments (CAP ).
ENV
(CAP ) = Σ (CAP ) = any (CAP ) ∪
O IC USE
any (CAP ) ∪
SYS
any (CAP ) ∪
AT
any (CAP )
ENV
NOTE 1 The union operation (∪) is used to indicate a composition (collection) of lower-level CAPs pertaining to a CAP.
Such compositions are further referenced as “Lower-CAP Linkages” for a specific CAP in this International Standard
(see Tables 2 and 3).
The CAP of each IC (user, system, AT, environment) is in turn composed of the CAP(s) of each of its
IC
Component Features (CAP ) that provide specifics of various directional communications and processes,
CF
these include: the CAP of each Input Receptor (IR), the CAP of each Output Transmitter (OT), and the
IR OT
CAP of each Processing Function (PF) involved in the IC. Describing PFs is optional for users and systems,
PF
but is required for ATs.
(CAP ) = Σ (CAP ) = any (CAP ) ∪
IC CF IR
any (CAP ) ∪
OT
any (CAP ) ∪
PF
ICs can make use of one or more OTs and/or IRs. Where multiple OTs or IRs are required they will be ANDed
within the CAP specification. Where substitutions of OTs or IRs are possible, they will be ORed within the
CAP specification.
NOTE 2 (IR1 AND IR2) is equivalent to (IR1, IR2).
EXAMPLE (IR1 AND (IR2 OR IR3)) requires that input receptor IR1 always be used and that either input receptor
IR2 or input receptor IR3 be used.
Systems are intended to help users to perform tasks. Systems might or might not be directly accessible by
users. The CAP of a system provides the starting point for evaluating and improving the accessibility of the
system for a user in a given environment. The Environment can reduce the accessibility of a system. ATs
might be used to increase the accessibility of a system. Thus, an evaluation of access involves analysing the
CAP(s) of a set of systems, users, environments, and ATs.
Figure 5 depicts the structure of the CAP. This four-level structure places CF Type-Specific Information [i.e.,
modality (CAP ), capability (CAP ), and processing (CAP )] within their own specific tables. Only those
M
C P
records that are applicable will be coded, leading to simplification and space saving.

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ISO/IEC 24756:2009(E)
CAP
O
CAP
IC
CAP
CF
CAP
M
CAP
C
CAP
P

Figure 5 — The CAP structure
6.3 Describing Overall CAPs
The overall CAP of a group of ICs shall be specified as outlined in Table 1. Every CAP specification has an
O
O
Identification Information section containing information such as the unique Name of the CAP , its Type (i.e.,
O
CAP ), and a Qualifier. It might also contain an unstructured narrative description. Narrative Descriptions can
O
be used to record preliminary information and/or provide an easy to read introduction to the structured details
of all CAP specifications. All useful CAP specifications have linkages to one or more CAP (s) and can have
O IC
linkages to other CAP (s).
O

Description Possible Values
Identification
Type The record type. CAP
O
Name An identifier of, or a commonly known any (must be unique within CAP)
name for, the CAP
O.
Qualifier A unary operator that qualifies this record one of
as being required, optional, or excluded. {SHALL
MAY
NOT}
Description A narrative description to record any
preliminary information and / or optional
comments further describing the object.
Linkages
Peer-CAP Peers to this CAP . {,
O O
,
…}
Lower-CAP The ICs used by this CAP . {,
IC O
,
…}

Table 1 — High level CAP structure
O

Linkages are described as pairs. The cap-name field is the name of the target CAP.
...