There are 3 primary gaps: structure, legibility and local change.

​Gaps by Category

The user needs fall into the groups. Changes that:
1. Require significant structural change to the presentation
2. Can be embedded in the overall block structure of the page.

The biggest gaps occur in needs that require significant structural change
to the presentation of content. These include: 3.2.1 Rewrap for One
Direction Scrolling, 3.2.2 Reflow to Single Column, 3.2.3 Line Length,
3.3.1 Text Size, 3.3.5 Size of All Elements, 3.4.5 Margins and Borders, and
3.4.6 Spacing Between Elements.

The remaining needs (excepting 3.5.1 Element Level Customization) can be
fit into almost any WCAG 2.0 compliant page organization.  These include:
3.1.1 Brightness Overall, 3.1.2 Text Contrast, 3.1.3 Not Relying on Color,
3.2.4 Hyphenation, 3.3.2 Font, 3.3.3 Style, 3.3.4 Capitalization, 3.4.1
Leading, 3.4.2 Letter Spacing, 3.4.3 Word Spacing, 3.4.4 Justification.
They support legibility for various populations.

Element level customization can require significant restructuring or not
depending if the change structure change, otherwise the can be embedded in
existing structure.

So here are the gaps:

In structural changes: rewrap (uni-directional scrolling) and reflow (one
column) are essential gaps.  They must be required and they are not.  UAAG
goes the farthest, but backs off on requiring these.  When these three gaps
are filled, line length, text size, size of all elements, margins and
borders, and spacing between elements will fall into place. That is, if
users can restyle after reflow and rewrap.

The remaining gaps could be summed up as involving insufficient capability
for users to choose typographic environment to support legibility. The
structure of the page will not change if the user wants other colors. On
bad pages, changing letter spacing make cause text to overlap a poorly
structured box, but most WCAG 2.0 content is robust enough to allow this
kind of change. This type of change boils down to letting the user choose
the font, font styles, colors, spacing and other typographic settings that
can improve the visual experience.  At present UAAG supports most of these
choices, WCAG does not.  Choice is necessary for low vision. It cannot be
optional.

Finally, we have element level customization that can apply to local style
or global structure. UAAG supports this for most features (size is
inadequate) but most others are present.  WCAG does not support this.

So as I see it we have three gaps:

Access to restructure the presentation, access to legibility, and access to
localize changes to the element level.

Sincerely, Wayne


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