WebAIM - Web Accessibility In Mind

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Re: how to detect images having math expressions

for

From: Steve Green
Date: Jun 4, 2008 6:30AM

Of course pages should be created and maintained so that they are
accessible. I hope none of us would disagree with that. However, the reality
is that there are millions of websites that were not created or maintained
that way. As an independent testing company that does not design or maintain
websites, 100% of our clients have existing websites that they wish to
assess and improve. Few if any are in a position to do a ground-up rebuild.

It is not helpful to say that an approach should not be considered just
because it is not 100% reliable. Nor is it helpful to state that sites
should be rebuilt or that every page should be tested. The question that we
and many other organisations face is how to make best use of the available
resources.

So I would be interested to know how you might approach the task of
assessing a 10,000 page website with a view to making the most beneficial
improvements within a budget and timescale that does not allow all pages to
be assessed. Or would you simply not undertake such a task, and leave it to
someone else to worry about.

Steve



-----Original Message-----
From: <EMAIL REMOVED>
[mailto: <EMAIL REMOVED> ] On Behalf Of Jukka K. Korpela
Sent: 04 June 2008 11:49
To: WebAIM Discussion List
Subject: Re: [WebAIM] how to detect images having math expressions

Steve Green wrote:

> I would agree with that but manually visiting every page simply isn't
> practical for large websites.

That's why "accessibility testing" is a fairly impractical concept in
general. Alt tags are just a small part (very small part, really) of the
problem.

Pages should be _created_ and maintained so that they are accessible.
Testing them for accessibility is usually not useful, except when there is a
well-defined realistic goal (e.g., testing 0,1 % of the pages of a large
site to prove that the site needs a redesign).

> I was thinking that a more
> cost-effective option might be to assess all the images and identify
> those that may need non-null 'alt' attributes.

Can't be done, I'm afraid.

> When you find out
> which pages use these images it may mean that perhaps only 10% of the
> pages need to be assessed for that checkpoint.

How come? We might _guess_ that, say, 1 by 1 pixel images need alt="", but
that's just a guess, and such images are often symptoms of accessibility
problems that should be studied, instead of blindly guessing that they are
ignorable images. Besides, such images aren't very popular these days, when
formatting can be better achieved using CSS.

I would say that even with a fairly sophisticated algorithm for
distinguishing "nullable" images from others, the percentage would rather be
90 %, and what would be the point then?

Jukka K. Korpela ("Yucca")
http://www.cs.tut.fi/~jkorpela/