[html4all] Headers= up

[Leif Halvard Silli]

2007-09-08 07:30:36 +0200 Robert Burns <rob at robburns.com>:
> On Sep 8, 2007, at 12:10 AM, Leif Halvard Silli wrote:
>> On 2007-09-08 06:36:23 +0200 Robert Burns <rob at robburns.com> wrote:

[ .. whwat the HTML4 algorithm says ... ]
>>> So the HTML 4 algorithm should not be including the Day 1, Day 2,,
>>> Day3, etc. headers. Though in fairness it also should not include
>>> the remarks and the other header cell in the THEAD< but I think that
>>> a generous reading of HTML4 would include those headers.
>> 
>> We must have the same amount of generousity to whichever spec we  read ;-) 
>> Perhaps that is the trouble? :-D
>> 
>> I am not certain you are correct here. What you quoted above is  merly step 
>> 1 of 5 possible steps in that algorithm.
> 
> This is the only relevant step in the algorithm for tables without  headers= 
> or axis=. The entire association happens in that step.


Rob, I think actually that algorithm only has *one* step. 

	HTML4 describes the algorithm in an unordered list. But when Ferg quotes it, he uses an ordered list. I just mention it because the formatting in HTML4 indicates that this list doesn't strictly describe the order in which the algorithm happens. E.g. consider the last list item, about TD cells with @AXIS being treated as header cells.  So all the HTML4 algorithm does is described inside the first item of that list. The other list items merely further explains some other limitations on how what is described in the first list item, is performed. (See full quote of the Algorithm at bottom of this letter.)

	The first list item describes one limitation of the search: when a data cell is found after a header cell. Fourth list item mention a further limititation, namely that the use of headers="" in a TH cell will also stop the search. Last list item mentions the last limitation, namely that a TD with @axis is also counted as header cell (i.e. it will be counted as a TH cell, I suppose)- and thus, if a data cell is found after the «axis-cell», then the search should stop at the axis cell as well.

Having said this, I now think that the basic Algorithm might not give us what we/Anne want in Anne's table. I think that he needs to use the scope="rowgroup" on the day 1, day 2 cells. And that he in addition must add scope="col" to the THEAD.

About @SCOPE in HTML4, the table inspector doesn't get that right either.

	But first an important thing, namely that HTML4 allows @SCOPE in TD cells as well. Because, as it says: «Note that it's not always possible to make a clean division of cells into headers or data. You should use the TD element for such cells together with the id or scope attributes as appropriate.»  As well as «Note the use of the scope attribute with the "row" value. Although the first cell in each row contains data, not header information, the scope attribute makes the data cell behave like a row header cell. This allows speech synthesizers to provide the relevant course name upon request or to state it immediately before each cell's content.» This is important, because, when you put @headers on a TD-cell, it will not stop the basic algorithm from working. 
	
	This last point isn't implemented in the table inspector - if you had <tr><td scope="row">, then the inspector shoul dhave listed this TD-cell as header for rest of the cells in that row. But that doesn't happen.

	Relating this to Anne's table: He could have used a TD instead of a TH in the Day 1, Day 2 cells. And no @scope or @headers. Then each TD cell would have seen the TH-s in the THEAD.

[ the basic algorithm in HTML4: ]
* First, search left from the cell's position to find row header cells.
  Then search upwards to find column header cells. The search in a given
  direction stops when the edge of the table is reached or when a data cell
  is found after a header cell.
* Row headers are inserted into the list in the order they appear in the
  table. For left-to-right tables, headers are inserted from left to right.
* Column headers are inserted after row headers, in the order they appear in
  the table, from top to bottom.
* If a header cell has the headers attribute set, then the headers
  referenced by this attribute are inserted into the list and the search
  stops for the current direction.
* TD cells that set the axis attribute are also treated as header cells.
-- 
leif halvard silli