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1.7 A definition of the functionality independent of CSS terminology

From: Wayne Dick <wayneedick@gmail.com>
Date: Tue, 24 Jan 2012 13:34:38 -0800
Message-ID: <CAJeQ8SA46nURe4GDxnju0nw7x7KoPdj-DH_g-D+dSPXr=r6GBQ@mail.gmail.com>
To: WAI-UA list <w3c-wai-ua@w3.org>, Shawn Henry <shawn@w3.org>, Jeanne Spellman <jeanne@w3.org>
1.7 Aims at the functional characteristics of  user CSS

HTML with CSS is the ideal model for providing visual access for
visual readers with low vision.  Why is this true? There are concrete
reasons for choosing this model over others, and for thinking of this
as the standard to promote for visual accessibility. The following
list of capabilities, denoted as simply SPIF, delineates why the
functionality of HTML with user CSS is ideal.

    S —Separation: HTML+CSS can implement complete separation of
visual presentation from meaning.  With care, this can be done
    P —Plasticity: CSS provides the full access to the typography used
to author documents. This enables a complete range of assistance that
is extensible as discoveries are made in assistive technology.
    I —Isomorphism: With HTML+CSS one can create a faithful
(one-to-one and onto mapping) from the author's visual semantics and
the visual semantics the user sees.  This means that the user's visual
semantics can be:
        perceivable by the user,
        appropriate for the user's reading needs,
        distinguishable as visual cues for semantic interpretation, and
        completely accurate.
    F —Freedom of Choice: Independently chosen CSS means that the user
does not need to ask permission of the author to see the document in a
usable format, so long the HTML browser supports user CSS.

It should be clear that any print format and rendering system that
claims to be accessible should support SPIF.  Separation makes
accurate transcription tractable; there is no need for artificial
intelligence.  Isomorphism means complete translation is possible.
Plasticity means accommodation can reach the full range of needs that
are known now or can be discovered in the future.  Freedom of choice
means that users with low vision can read content (sometimes private
information) without having to depend on another person for help.
Where 1.7 Succeeds and Fails

The concept of a user style sheet is misleading when it used in the
context of assistive technology.  I and a handful of people (most of
whom I know), actually write style sheets to accommodate the reading
needs of people with low vision.  It is too hard to justify user style
sheets if we think of the end user as being the author of the CSS.
There are just to few of us.  The appropriate and genuinely
descriptive term should be assistive style.  This would indicate a
style structure that is authored by a professional and constructed to
meet the needs of the individual end user.  So, user style sheet is a
poor designation of this assistive technology, and it actually
promotes the notion that access to SPIF is impractical.

Once we expand our vision from user style sheet to assistive style
data structures that are probably not be authored by the user, we see
that 1.7 can be represented in a way that is both practical and
extensible.  We must write the success criteria to incorporate SPIF,
independent of the underlying medium.

As far as the accessibility they provide, user style sheets are the
best thing there is to promote access for visual readers with low
vision.  Right now few have access to user style sheets, so
implementers of user agents tend to make their priority low.  Every
electronic print medium needs the capability of user style sheets.  We
need to present 1.7 and sell it in a form that is SPIF.

That's All Folks,
Received on Tuesday, 24 January 2012 21:35:13 UTC

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