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chaining @headers and cycles [was: Re: function and impacts...]

From: Al Gilman <alfred.s.gilman@ieee.org>
Date: Sun, 5 Oct 2008 10:11:48 -0400
Message-Id: <1C06A45D-9461-4FAC-A3EA-26431689A9B7@ieee.org>
Cc: joshue.oconnor@cfit.ie, Laura Carlson <laura.lee.carlson@gmail.com>, James Craig <jcraig@apple.com>, Chris Wilson <Chris.Wilson@microsoft.com>, W3C WAI-XTECH <wai-xtech@w3.org>, public-html@w3.org, Gez Lemon <gez.lemon@gmail.com>
To: Henri Sivonen <hsivonen@iki.fi>


On 25 Sep 2008, at 4:24 AM, Henri Sivonen wrote:
>> [...]
>
> Here's an example of a table with at least one headers/id cycle:
> http://www.usdoj.gov/jmd/fass/afvreport2005.htm
>
> Regardless of how common this is, if headers cells can be chained  
> AND authors can add arbitrary header associations, it is *possible*  
> to construct a cyclic header chain. A proper spec must, then,  
> define in detail what an agent is to do with cycles.

Here's one processing rule that I would submit for consideration:

Grow a running set of the nodes that are included in self 
+recursivelyRelatedBy@headers.  When an @headers arc (one ID
appearing in an @headers attribute) leads to a node
already in that set, drop _that arc_ (quietly) and continue to
follow the rest.

This allows for mutual dependency without creating
a non-terminating process.

> (What does existing client software do, btw?)

I'll try to get this confirmed, but AFAIK the present implementation
does not chain @headers references.  I just reads, when asked, the
contents of the cells mentioned in the @headers of the cell where
the focus was when the AT was asked for more info.  Maybe in  
conjunction with the first-in-row, first-in-column heuristic headers.

Al

> -- 
> Henri Sivonen
> hsivonen@iki.fi
> http://hsivonen.iki.fi/
>
>
>
Received on Sunday, 5 October 2008 14:12:35 GMT

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