1. Personal Needs and Preferences
Properties
#
User preferences are defined to support web authors in delivering a
best-fit match from resources available to a person's needs expressed in
terms of modalities the user can receive. Not all content can readily
meet a user's needs in every context but where preferences are available
a better match might be made than where they are not. Matching a user's
explicitly-expressed needs might require changing configurations on a
delivery device, reporting to a web app what those preferences are and
adaptations the device has made to them and the web app may itself
change configuration and may fetch and deliver alternative content to
meet the needs.
In some cases a preference might be addressed directly and completely
by a device. In some cases a device may partially address a preference
and further support for that preference will need to be provided by a
web app and in some cases the web app will address the preference. This
is likely to be different for each preference, device, environmental and
other context.
1.1 Processing of Preferences
In this section we present an example as an introduction, ahead of its
full definition.
This specification provides a number of Preference Property Definitions
expressed in terms of sensory modalities and recognised adaptation
types. Each preference property instance consists of a (space-separated
unordered) list of tokens taken from a strict vocabulary for
that property. For example the preference
textualForAuditory
#
indicates a user wishes auditory resources to be replaced by or augmented
by textual resources. This may be done in different ways depending on the
media context. Its values are a list drawn from the vocabulary:
(true false captions transcript
transcript-simultaneous)
Token Values
|
Description |
true |
A preference that audio modalities are replaced or augmented by
textual ones |
false |
Default value - no preference |
captions |
A preference that captions be delivered simultaneously with the
audio |
transcript |
A preference that video be replaced by a transcript. |
transcript-simultaneous |
A preference that a transcript be delivered at the same time as
audio or video |
If the property has a value of '(true)' this is to be interpreted as a
general requirement and a textual form delivered that is appropriate for
the media concerned drawn from other tokens in that vocabulary as
appropriate to the media context. A value of (captions) or (true
captions) is to be interpreted as that the user wishes for audio to be
accompanied by captions. It implies that the property is true and an
intelligent system might infer that if captions are not available but a
transcript is then this might be useful to deliver instead even though the
user has not requested it explicitly. The token 'false' must occur alone
so a list of tokens containing 'false" and any other value is undefined
(this includes '(true false)'. The application should provide the best
match to the user's preferences.
1.2 Organisation of Preference Properties
Properties are described in terms of the modalities to which they
relate. There are two kinds:
- Properties that relate to delivery of a specific modality - for
example highContrast relates to a visual modality.
- Properties that relate a preferred modality to an existing one and
optionally give specific adaptation types that are preferred.
An instance of a property consists of a (space separated, unordered)
list of tokens drawn from a vocabulary for that property.
Where a property preference is for one modality over another delivery may
be augmenting the one modality with another or replacing it depending on
the best match to the user's context, which may be determinable from other
preference settings. For example a user may specify that they prefer
auditory information be delivered in textual form with the setting
textualForAuditory : true
A textual alternative might be delivered to the user instead of the audio
or displayed simultaneously with rendering the audio. Note that some users
find considerable benefit from simultaneous rendering of resources in
multiple modalities, particularly but not exclusively users with
particular cognitive disabilities, non-native language speakers and
language learners. The choice of whether to render the text
simultaneously with the audio might be made by matching also to a user's
language preferences or by the context of the media possibilities.
Each property instance has a value that consists of a list of tokens as
specified in the definition of properties. Each token has an optional list
of refinement parameters where such is meaningful.
1.2.1 Interpretation of values
[Editors note: This needs a little careful work to tighten it - for
example for some vocabulary (true false X Y) is the instance (true)
equivalent to (X Y) ? ]
Lists of values may not be logically inconsistent. In particular the
following are prohibited and if they occur are undefined:
- Any list of values containing both true
and false
- Any list of values containing false
together with any other value (i.e. false
must occur alone)
- A list of values consisting of (true X) should be considered
equivalent to (X)
Where a list of values contains
true
and any other values the other values should be considered as refining the
value true (i.e. providing more detail of what is preferred). A system
responding to the value for some property of
(true)
might make intelligent inferences about media that might be useable by
that user in that context. Where a vocabulary contains terms (true,
false, X, Y) and an instance of a property is either (true, X) or just (X)
a system would ideally deliver an X if it is available but if an X is not
available then the system might infer that a Y would be useful and deliver
that instead.
1.3 Preference Property Definitions
-
1.3.1 auditory
#
Indicates a preference for auditory resources
Token Values
|
Description
|
true
|
Prefer auditory resources
|
false
|
Default value - no preference |
Examples:
-
1.3.2
textual
#
Indicates a preference for textual resources
Token Values
|
Description
|
true
|
Prefer textual resources
|
false
|
Default value - no preference |
Examples:
-
1.3.3 visual
#
Indicates a preference for visual resources
Token Values
|
Description
|
true
|
Prefer visual resources
|
false
|
Default value - no preference |
highContrast |
Where visual is the preferred modality the preference is for
presentation of text and images of text that has a contrast ratio
of at least 4.5:1, or, for larger text, a contrast ratio of at
least 3:1 (WCAG2 Checkpoint 1.4.3):
http://www.w3.org/TR/WCAG20/#visual-audio-contrast. |
blackOnWhite |
black text and borders on a white background |
whiteOnBlack |
white text and borders on a black background |
inverseVideo |
Text, image and video colors reversed |
Examples:
-
1.3.4 tactile
#
Indicates a preference for tactile resources
Token Values
|
Description
|
true
|
Prefer tactile resources
|
false
|
Default value - no preference |
Examples:
-
1.3.5
textualForAuditory
#
Indicates a preference that an auditory resource or presentation be
augmented by or replaced by a textual one
Token Values |
Description |
true |
A preference that audio modalities are replaced or augmented by
textual ones |
false |
Default value - no preference |
captions |
A preference that captions be delivered simultaneously with the
audio |
transcript |
A preference that video be replaced by a transcript. |
transcript-simultaneous |
A preference that a transcript be delivered at the same time as
audio or video |
Examples:
-
1.3.6 textualForVisual
#
Indicates a preference that a visual resource or presentation be augmented
by or replaced by a textual one
Token Values |
Description |
true |
A preference that visual modalities are replaced or augmented by
textual ones |
false |
Default value - no preference |
alternativeText |
A preference for alternative text instead of or together with a
resource wth visual modality (typically an image) |
longDescription |
A preference that a visual modality resource be replaced by or
augmented by a longDesc. |
Examples:
-
1.3.7 textualForTactile
#
Indicates a preference that a tactile resource or presentation be
augmented by or replaced by a textual one
Token Values |
Description |
true |
A preference that tactile modalities are replaced or augmented
by textual ones |
false |
Default value - no preference |
Examples:
-
1.3.8 visualForAuditory
#
Indicates a preference that an auditory resource or presentation be
augmented by or replaced by a visual one
Token Values |
Description |
true |
A preference that auditory modalities are replaced or augmented
by visual ones |
false |
Default value - no preference |
signLanguage |
A preference that an auditory resource be replaced by or
augmented by a sign language presentation, as defined above [TBD
url to defin] |
Examples:
-
1.3.9 visualForTactile
#
Indicates a preference that a tactile resource or presentation be
augmented by or replaced by a visual one
Token Values |
Description |
true |
A preference that tactile modalities are replaced or augmented
by visual ones |
false |
Default value - no preference |
Examples:
-
1.3.10 visualForTextual
#
Indicates a preference that a textual resource or presentation be
augmented by or replaced by a visual one
Token Values |
Description |
true |
A preference that textual modalities are replaced or augmented
by visual ones |
false |
Default value - no preference |
Examples:
-
1.3.11 auditoryForVisual
#
Indicates a preference that an visual resource or presentation be
augmented by or replaced by an auditory one
Token Values |
Description |
true |
A preference that visual modalities are replaced or augmented by
auditory ones |
false |
Default value - no preference |
audioDescription |
A preference that a visual resource (typically the visual
component of a video) be replaced by or augmented by an audio
description. Note that in some countries this is referred to as
'videoDescription'. |
Examples:
-
1.3.12
auditoryForTactile
#
Indicates a preference that a tactile resource or presentation be
augmented by or replaced by an auditory one
Token Values |
Description |
true |
A preference that tactile modalities are replaced or augmented
by auditory ones |
false |
Default value - no preference |
Examples:
-
1.3.13 auditoryForTextual
#
Indicates a preference that a textual resource or presentation be
augmented by or replaced by an auditory one
Token Values |
Description |
true |
A preference that textual modalities are replaced or augmented
by auditory ones |
false |
Default value - no preference |
Examples:
-
1.3.14 tactileForAuditory
#
Indicates a preference that an auditory resource or presentation be
augmented by or replaced by an tactile one
Token Values |
Description |
true |
A preference that auditory modalities are replaced or augmented
by tactile ones |
false |
Default value - no preference |
Examples:
-
1.3.15 tactileForVisual
#
Indicates a preference that a visual resource or presentation be augmented
by or replaced by a tactile one
Token Values |
Description |
true |
A preference that visual modalities are replaced or augmented by
tactile ones |
false |
Default value - no preference |
Examples:
-
1.3.16 tactileForTextual
#
Indicates a preference that a textual resource or presentation be
augmented by or replaced by a tactile one
Token Values |
Description |
true |
A preference that textual modalities are replaced or augmented
by tactile ones |
false |
Default value - no preference |
Examples:
-
1.3.17 languageOfAdaptation
#
Indicates a preference for adaptations to be delivered in a particular
language. Note that this may not be the same language in which the user
operates the device.
Token Values |
Description |
Internal Language Code presented to user as
string or selectable widget |
TBD: get IETF reference |
undefined |
Preference is for adaptations to be delivered in the default
user language for that device |
Examples:
-
1.3.18 hazard
#
Indicates characteristics of resources that a user DOES NOT wish to
receive because of potential hazards for that user. Note also that the
meaning of a value of true without any other value is undefined for this
property (i.e. it must have a refinement to be meaningful)
Token Values |
Description |
false |
Default value - no preference |
flashing |
A preference that a resource having a visual pattern that
flashes more than three times in any one second not be delivered
to the user. Note that this level of flashing can cause seizures
in some users (WCAG2 Guideline 2.3.1 A):
http://www.w3.org/TR/WCAG20/#seizure]. |
flashingStrict |
A preference that a resource having a visual pattern that
flashes more than three times in any one second not be delivered
to the user. Note that this level of flashing can cause seizures
in some users (WCAG2 Guideline 2.3.1 AAA):
http://www.w3.org/TR/WCAG20/#seizure |
motionSimulation |
A preference that a resource simulating motion not be delivered
to the user. Note that for some users such a resource may induce
nausea |
sound |
Prefer
that
resources generating an audio pattern that can cause the user to
have seizures [ISO 29138] not be delivered to the user. |
Examples:
-
1.3.19 ATInteroperable
#
Indicates that where possible resources that are interoperable with AT
should be selected. Note that the default for this preference unless
otherwise defined is true.
Token Values |
Description |
true (default)
|
Resources that are interoperable with AT should be selected
whenever possible. Interoperability is indicated by compliance
with WCAG 2.0 checkpoints: 1.1.1, 1.3.1, 1.3.2, 2.4.4, 3.1.1,
3.1.2, 3.3.2, 4.1.1 and 4.1.2.
|
false |
explicit preference excluding this requirement
|
Examples:
-
1.3.20 simplePresentation
#
Indicates a preference for very simple presentation of interface and
content even if the device supports more complex presentation (for example
if the device large or high-resolution screen)
Token Values |
Description |
true |
A preference for presentation to be of a similar level of
complexity to that commonly delivered to small screen devices
using agile design - typically no more than six controls or
regions of interest on a page. |
false |
Default value - no preference |
Examples:
Deliver the mobile device presentation of a web site to a desktop device
1.4 Terms Used in the Definition of the User
Preference Properties
#
The following terms are used in the definitions in this
specification:
alternativeText
- Text that is programmatically associated with non-text content and
that serves the equivalent purpose (WCAG2).
- http://www.w3.org/TR/WCAG20/#text-altdef;
- http://www.w3.org/TR/WCAG20/#text-equiv.
audioDescription
- Narration that has been added to a soundtrack to describe
important visual details that cannot be understood from the main
soundtrack alone (WCAG2). Note that in some countries this is referred
to as 'videoDescription'
- http://www.w3.org/TR/WCAG20/#audiodescdef.
- Might be further refined as enhanced.[to be done link to defn of
enhanced]
auditory
- Information is conveyed that requires the sense of hearing.
- May be refined with the detail recorded or synthesised
blackOnWhite
- black text and borders on a white background
captions
- Synchronized visual and/or text alternative for both speech and
non-speech audio information needed to understand the media content
(WCAG2):
- http://www.w3.org/TR/WCAG20/#captionsdef
- Might be further refined as enhanced or realtime [TDB link to
defns]
e-book
- Electronic book, a book published in electronic form:
- http://en.wiktionary.org/wiki/e-book
flashing
- A visual pattern that flashes more than three times in any one
second; this level of flashing can cause seizures in some users
(WCAG2 Guideline 2.3.1 A):
- http://www.w3.org/TR/WCAG20/#seizure
flashingStrict
- A visual pattern that flashes more than three times in any one
second; this level of flashing can cause seizures in some users
(WCAG2 Guideline 2.3.2 AAA):
- http://www.w3.org/TR/WCAG20/#seizure
haptic
- Of, or relating, to the sensation of touch; used here to identify
resources that include force feedback or other three-dimensional
interfaces:
- In part from http://www.webopedia.com/TERM/H/haptic.html.
Linguistic Indicator:
highContrast
- Visual presentation of text and images of text that has a contrast
ratio of at least 4.5:1, or, for larger text, a contrast ratio of at
least 3:1 (WCAG2 Checkpoint 1.4.3):
- http://www.w3.org/TR/WCAG20/#visual-audio-contrast.
inverseVideo
- Text, image and video colors reversed
longDescription
- An alternative text that is longer than a few sentences.
motionSimulation
- Content that simulates motion; this may result in a feeling of
nausea to the user.
signLanguage
- A language using combinations of movements of the hands and arms,
facial expressions, or body positions to convey meaning (WCAG2):
- http://www.w3.org/TR/WCAG20/#sign-languagedef.
simplePresentation
- A presentation of a similar level of complexity to that commonly
delivered to small screen devices using agile design - typically no
more than six controls or regions of interest on a page.
sound
- An audio pattern that can cause the user to have seizures [ISO
29138].
tactile
- Information is conveyed that requires the sense of touch.
textual
- Information is conveyed that requires the processing of text
transcript
- A written, typewritten, or printed copy; something transcribed or
made by transcribing:
http://dictionary.reference.com/browse/transcript.
visual
- Information is conveyed that requires the sense of vision.
whiteOnBlack
- white text and borders on a black background
1.5 Term Refinements
Some terms, when used as values of a property, may have accompanying
detail refinements or parameters giving further preference detail.
enhanced
- An adaptation with more extensive forms of alternative than the
standard for that kind of adaptation; enhanced captions might
include images or speech bubbles, and enhanced audio description
might pause the video to insert extra audio.
realTime
- An adaptation produced at the time a resource is being produced;
real-time captions are often used for live newscasts.
recorded
- An audio adaptation featuring a human voice reading the material.
synthesized
- An audio adaptation featuring text-to-speech technology.
verbatim
- An exact transcription of audio; verbatim captions or verbatim
transcripts capture all speech word for word.
1.6 API, Data Structures and Implementation Strategies
[TO DO]
1.7 Possible Future Work
 Preferences for personalisation of educational assessment ?
#