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Re: Images and alternative text

From: James Graham <jg307@cam.ac.uk>
Date: Thu, 07 Aug 2008 21:43:25 +0100
Message-ID: <489B5E6D.5050008@cam.ac.uk>
To: Ian Hickson <ian@hixie.ch>
CC: Philip Taylor <pjt47@cam.ac.uk>, "public-html@w3.org" <public-html@w3.org>

Ian Hickson wrote:
> On Thu, 7 Aug 2008, Philip Taylor wrote:
>   
>>   <img src="..." alt="{x \over y} = {1 \over {y \over x}}">
>>     
>
> ...would be a horrific alternative text to give a screen reader.
>   
I'm not an expert on the accessibility of different representations of 
mathematics but I would imagine that LaTeX source would be well 
supported by AT designed for working with maths.  Indeed there is some 
evidence that this is the case [1]. Therefore a user encountering this 
fragment of LaTeX could copy it to an appropriate AT for rendering. For 
the case of advanced maths I would expect many of the subset of users 
interested in the content at all to be able to mentally reconstruct the 
semantics from LaTeX source code more easily than from almost any other 
form.
> I don't think it's equivalent to the image at all. It's the source of a 
> program that was used to generate the image, but that's not the same 
> thing. Would you consider the replacement text of a fractal to be the C 
> source code that generated it? Or the replacement text for an SVG file to 
> be the raw source code of that SVG file?
>
> Correct alternative text for an image generated by LaTeX is a textual 
> representation of the expression generated from the same LaTeX.
>
> e.g.:
>
>    <img src="..." alt="The fraction x over y is equal to 1 divided by the 
>    fraction y over x.">
It's impractical to expect people to do this if the method of generating 
the page is conversion of TeX-like source to HTML (which it almost 
always is), especially for complex expressions (there is a reason for 
using a symbolic language after all). I don't think that making the 
low-effort solution break at random on the basis that people should use 
a solution that is orders of magnitude more effort is going to improve 
overall accessibility.

Even without this specific example I think using random microsyntaxes in 
existing attributes is a bad idea for the reasons Phillip mentioned.

[1] http://theoval.sys.uea.ac.uk/~nlct/latex/#access
Received on Thursday, 7 August 2008 20:44:01 GMT

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