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Re: Media type recognition by HTML user agents

From: Jason White <jasonw@ariel.ucs.unimelb.EDU.AU>
Date: Sat, 25 Oct 1997 10:36:21 +1000 (AEST)
To: WAI HC Working Group <w3c-wai-hc@w3.org>
Message-ID: <Pine.SUN.3.95.971025102544.12303A-100000@ariel.ucs.unimelb.EDU.AU>
On Fri, 24 Oct 1997, Daniel Dardailler wrote:

> 
> > If any parameters are added to the base type which the user agent can not
> > interpret, then the resource to which the media type relates (E.G. a style
> > sheet) should not be accessed.
> 
> I'm a little confused by the position taken here.
> 
> If I get a document with a pointer to a media="braille embossed" CSS
> file and HTML and my CSS setup only defines "braille", am I suppoed to
> ignore it altogether ?
> 
This is indeed what I had in mind, since the user agent can not in such a
case determine whether the output medium satisfies the requirements of the
style sheet. The problem can be exemplified as follows:

media="braille displayed 80" (a style sheet for an 80-cell braille
display).

Suppose that the user agent does not recognise the parameters, and
truncates the media type to:
media="braille"
and the output device is a braille embosser with a maximum of 40
characters per line. The style sheet includes properties that require text
to be positioned horizontally in columns 41-80.

Another solution, which might perhaps be better, would be to access the
style sheet, ignore the extra media type parameters, and then activate
error checking to ensure that none of the style properties results in
output that would exceed the capabilities of the hardware.

I do not recall reading any discussion of such error checking in the CSS
specification, but I may have overlooked it.
Received on Friday, 24 October 1997 20:36:43 UTC

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