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Re: Linearizing Tables

From: Steven McCaffrey <smccaffr@MAIL.NYSED.GOV>
Date: Mon, 17 Apr 2000 11:42:20 -0400
Message-Id: <s8faf8c2.095@mail.nysed.gov>
To: <charles@w3.org>
Cc: <kford@teleport.com>, <w3c-wai-ig@w3.org>

Hi Charles:
     Thank you for some needed clarifications and
linking related issues. 

"The value of a table is being able to analyse data in two dimensions"

Maxima and minima I grant is not such a good example, you are correct.
Could you give some examples of
analyzing data in two dimensionss that might be lossed by the linear version?
My less than optimal choice of example should not distract from the overall point I am making,
that there are such cases where a llinearized version does not provide equivalent information.  Having a large set of specific cases where this is true could at least help
designers who use data tables to write a more helpful description with the Summary or Caption attributes or Description link.
      Also, understanding this point is an excellent case in point to distinguish 
between content and presentation.  sometimes we all get used to a given presentation, so much so that we forget it is just
a presentation, and one particular presentation, and not the underlying information or information structure.
That is, we think the presentation is the very definition
of the object (data and relationships) we are communicating.
Color is another example (although maybe a less than optimal one!
Red means stop.  No, it is a relatively widespread customary association with the word stop, but not
necessarily the case.  This is the reason for the checkpoints about not using color alone.
What all this boils down to is I think there is a need for many many more examples of what is
"presentation" and what is not.
Actually, I would go so far as to say the distinction between "object" and "representation", at least within the computer environment,
is a false dichotomy.  There are only representations that vary along a spectrum of relative stability based on
standards and/or custom.
ASCII itself is just a representation, albeit a very standard, stable (at least so far!)
representation.  The mapping from the ASCII code to a set of pixeles on the screen is, of course, also another representation.
This latter step now entails a mapping from a representation to a representation, perhaps it could be called a 
"second order" representation.  It too is arbitrary on some level, although, since it has a relatively standard set of mappings (i.e. fonts), we sometimes forget this.

This is why sighted people also use graphics a lot - the shape of a curve
constructed from data points makes some things very easy to find."

Yes, which is why I referenced the earlier thread, when I said,  
"All this, in a slightly different context, I have raised before in the How to describe flowcharts, ... thread."
Could you give examples of
exactly what things are made easy to find with a graph?

     I would like to see a much expanded list of examples in the next version of the WCAG.
I think such a set would go a long way to help
explain the differences between presentation and content/structure.
     I also alluded to XML.
Are there any XML/XSL/SVG solutions 
that can be implemented on 4.0 or 5.0 browsers today?
There may even be a need to create a separate XSL or SVG based solution for different types of tables and/or graphs,
(bar charts,,,, pie charts, histograms, function plots, etc.).
I've seen the specs and related theoretical discussion.  
Are there working examples?


Steve McCaffrey
Senior Programmer/Analyst
Information Technology Services
New York State Department of Education
New York State Workgroup on Accessibility to Information Technology 
Web Design Subcommittee 

>>> Charles McCathieNevile <charles@w3.org> 04/14/00 05:01PM >>>

a good analysis of the problem, although it makes a fe assumptions that don:t
reflect my own experience.

The value of a table is being able to analyse data in two dimensions
reasonably easily. But they are not really easy to inspect - in many cases a
linearised version is a better place to look for maxima and minima, and some
other fetures.

This is why sighted people also use graphics a lot - the shape of a curve
constructed from data points makes some things very easy to find.


Charles McCN

On Mon, 10 Apr 2000, Steven McCaffrey wrote:

  Hi Kelly:
   A very good example illustrating many existing problems.
       As pointed out in a previous thread, 
  the example table in the techniques document of the table of cups of coffe consumed by each senator does *not*
  transform  as described, using JFW 3.2.  I don't know if JFW 3.5 transforms it as described.
  Even if it does, developers should not assume all users have JFW,
  nor that all JFW users have the latest version. 
  If the row and column headings were  spoken before the cells, this would be an adequate linearized version.  However, I still maintain that an adequate  linearized version of a table does not provide equivalent access, although it 
  does provide  a barely minimum degree of access.
  The following applies to      data tables.
  Linearized tables do not provide equivalent access.  Otherwise, why do sighted people use a two dimensional visual presentation and not a linear list of the cells? 
  In other words, if a person were to read a large data table to a friend over the phone, one cell at a time, would the person listening to the verbal enunciation of the table feel that he/she is getting the information out that she/he wants from the table?
  Clearly not.  What would happne in this case?
  The person listening would no doubt ask to have certain cells or even entire rows read out again, without having to listen to the entire table again, one cell at a time.  For data tables containing numerical data,(unlike the landsend.com example),  
  the listener might ask the reader  at the other end of the phone to answer a question like
  "How does the values of X change over time?  Is there a pattern?  Where does it reach a maximum..."
  In a table like that in the landsend.com example, if prices are also listed, one might want to ask,
  "What is the cheapest , most expensive etc." just to name a few questions I might want to ask.
  Another class of question might be "Is there product x in size range Y?" 
  All this, in a slightly different context, I have raised before in the How to describe flowcharts, ... thread.
  all this information could be provided in a long describption ahead of time, or by
  some interactive database-like query, (XML to the rescue?).
       Until such descriptions or interactivity exists, access to data tables is not equivalent,
  linearized or not.  And the fact of the matter is that still,
  many, if not most, screen readers do not even provide a correct linearized version for all tables.
      I accept a correctly linearized version of data tables as only an interim solution
  and hope the W3C WAI is still working on truly equivalent access to data tables.
  Tables are going to be used more and more, especially in data intensive areas like statistical or budgetary information.
  The overall principle boils down to the fact that a two dimensional visual representation 
  of a table is incorrectly assumed to be the definition of a table, and is thus,
  by its very nature, confusing presentation with logical structure.
  The definition used in the WCAG of "tabular information" is, very roughly, correct, and yet
  the WCAG and techniques documents still insist that a linearized version is accessible.
  As I said, a linearized version provides a bare minimum degree of access but falls far short of equivalent access.
Received on Monday, 17 April 2000 11:43:57 UTC

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