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Re: A look at tables

From: Ian Jacobs <ij@w3.org>
Date: Mon, 20 Dec 1999 21:52:17 -0500
Message-ID: <385EEB61.E9ACDF7E@w3.org>
To: Scott Luebking <phoenixl@netcom.com>
CC: w3c-wai-ua@w3.org
Scott Luebking wrote:
> Hi,
> Maybe a way to look at tables is to forget the presentation and think
> of them in terms of navigation.  I believe that it will not be possible
> to bind all the different navigation possibilities to individual
> keystrokes (though it would be possible to do that for the more
> frequent table navigation actions).  

> For example, there should be the
> ability to go directly to a specific cell which would require
> multiple keystrokes.  Similarly, the ability for full relative movement,
> e.g. left 7 columns and down 43 rows, will need multiple keystrokes.

I'll add relative "direct" navigation to the techniques.
> So, any table navigation should support specifying the navigation
> by multiple keystrokes.

I'm not sure if I agree with that. I think the number of keystrokes
is separate from the functionalities you describe.
> Another question to ask is whether the table navigation can be expressed
> in a closed symbolic form.  This is helpful in analyzing the complexity
> of the navigation expression.  (Sorry about bringing in some computer
> science here.)  I believe much of the table navigation can be described by:
>     [h|m|f] [+|-] [n|$] , [+|-] [n|$]
> where:
>     h  -  header area
>     m  -  main area
>     f  -  footer area
>     n  -  a string of digits
>     $  -  last row or column
> Direct cell navigation is expressed by not including the signs.  Relative
> cell navigation is specified by including the signs.  Mixed navigation
> is also supported.  

What is "mixed navigation"?

> So any navigation system which can be shown to map into
> this representation would be rather complete.
> A table navigation problem is to what cell does the user go when moving
> out of a span cell.  For example, if the span cell is three columns
> wide, to which cell does the user go when they choose to go down.

To the row below..

> Similarly, if the user is in a cell in a row with 5 columns, but the
> next row with 5 columns is 7 rows down, where does the user go when they
> go down?  I think navigation could be simpler by navigating through a
> different concept of a table.  Instead of using the HTML table as the
> basis of navigation, a "normalized" table could be used onto which the
> HTML table is mapped.  (I'm sorry about getting abstract here, but I
> think it does actually simplify some of the navigation issues.)  A
> normalized table is one where all the rows have the same number of
> columns and all the columns have the same number of rows.  Each cell in
> an HTML table maps into one or more cells in the normalized table.  A
> span cell in an HTML table occupies a set of continous cells in the
> normalized table.  For example, if a span HTML cell spans 3 columns and
> two rows, it would map into a block of cells 3 columns wide and two rows
> high in the normalized table.

Yes, I think it would be disorienting to move from row N down one row
and find yourself in row N + 20. Instead, you might have to have
to have your position adjusted left or right. Cells (in the HTML model)
start in the row / column position where they are specified. They may
extend into the row or column (left or right depending on the table
In the case you describe above, I'd move the focus down one row
into the cell that happens to span that row.

That's how emacs seems to work when I move the cursor up and down
among lines of text of differing lengths (although I'm sure
this is configurable): If horizontal position N exists in line L + 1,
move the curor from L(N) to L+1(N). If not, move it from L(N) to

 _ Ian

 - Ian

Ian Jacobs (jacobs@w3.org)   http://www.w3.org/People/Jacobs
Tel/Fax:                     +1 212 684-1814
Cell:                        +1 917 450-8783
Received on Monday, 20 December 1999 21:52:42 UTC

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