I am reviewing a set of pages, some of which include in-line mathematical
formulas represented as images. I am addressing the accessibility issues
behind those images. (Conformance to Section 508 of the applicable US
government regulations is required.) Ick--at least, I suppose, until MathML
is generally supported.
One approach would be to set the ALT attribute to be a linearized version of
the equation. But this gets to be tough if there are multiple levels of
fractions or exponents. For example, here is a linearized version of a
normal probability density function:
(1/σ√ (2π))e^(&min us;(x − μ)^2/(σ^2))
ISSUE 1: Many formulas can't be linearized effectively, at least if they are
to be kept in mathematical form.
ISSUE 2: Can speech synthesizers even handle these? For example, if I use
symbol ≓ and the user agent speaks Unicode, it's going to read "image
of or approximately equal to" every time it sees this symbol. This seems
overly burdensome for the user. Another strategy would be to spell
everything out in words, as though I were reciting the expression:
One over sigma times the root of 2 pi, times e to the power
of the negative square of (quantity) x minus mu (close quantity)
over the square of sigma.
But then, in IE and Netscape 4.7, this would appear in a bubble and look
awful.
ISSUE 3: Is there yet a different set of considerations for users of Braille
displays? Or are they comparable to those of users of speech synthesizers?
ISSUE 4: So I wondered: what if I used both ALT and TITLE attributes on the
same image? I could put a single blank space in the title and a linearized
formula the alt. Or a single blank space in the title and a recitation in
the alt. Or a linearized formula in the title and a recitation in the alt.
I determined that when an <img> tag has alt text AND a non-trivial title, IE
6 pops up the title; Netscape 4.7 pops up the alt text; and Netscape 7 and
Mozilla pop up the title.
When an <img> tag has alt text, and a title attribute consisting of a single
space, IE 6 pops up a tiny, empty bubble; Netscape 4.7 pops up the alt text;
and Netscape 7 and Mozilla don't pop up anything at all (which seems to be
the best result of all).
I'm wondering how any of this combinations will play out in:
Text browsers, or graphical browsers with images turned off;
Speech-synthesizing or Braille readers for mainstream browsers;
Speech-synthesizing user agents;
Braille-based user agents (are there any?)
Are any of you familiar with these issues?
--
Harlan Messinger
Remove the first dot from my e-mail address.
Veuillez ôter le premier point de mon adresse de courriel.
formulas represented as images. I am addressing the accessibility issues
behind those images. (Conformance to Section 508 of the applicable US
government regulations is required.) Ick--at least, I suppose, until MathML
is generally supported.
One approach would be to set the ALT attribute to be a linearized version of
the equation. But this gets to be tough if there are multiple levels of
fractions or exponents. For example, here is a linearized version of a
normal probability density function:
(1/σ√ (2π))e^(&min us;(x − μ)^2/(σ^2))
ISSUE 1: Many formulas can't be linearized effectively, at least if they are
to be kept in mathematical form.
ISSUE 2: Can speech synthesizers even handle these? For example, if I use
symbol ≓ and the user agent speaks Unicode, it's going to read "image
of or approximately equal to" every time it sees this symbol. This seems
overly burdensome for the user. Another strategy would be to spell
everything out in words, as though I were reciting the expression:
One over sigma times the root of 2 pi, times e to the power
of the negative square of (quantity) x minus mu (close quantity)
over the square of sigma.
But then, in IE and Netscape 4.7, this would appear in a bubble and look
awful.
ISSUE 3: Is there yet a different set of considerations for users of Braille
displays? Or are they comparable to those of users of speech synthesizers?
ISSUE 4: So I wondered: what if I used both ALT and TITLE attributes on the
same image? I could put a single blank space in the title and a linearized
formula the alt. Or a single blank space in the title and a recitation in
the alt. Or a linearized formula in the title and a recitation in the alt.
I determined that when an <img> tag has alt text AND a non-trivial title, IE
6 pops up the title; Netscape 4.7 pops up the alt text; and Netscape 7 and
Mozilla pop up the title.
When an <img> tag has alt text, and a title attribute consisting of a single
space, IE 6 pops up a tiny, empty bubble; Netscape 4.7 pops up the alt text;
and Netscape 7 and Mozilla don't pop up anything at all (which seems to be
the best result of all).
I'm wondering how any of this combinations will play out in:
Text browsers, or graphical browsers with images turned off;
Speech-synthesizing or Braille readers for mainstream browsers;
Speech-synthesizing user agents;
Braille-based user agents (are there any?)
Are any of you familiar with these issues?
--
Harlan Messinger
Remove the first dot from my e-mail address.
Veuillez ôter le premier point de mon adresse de courriel.
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