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Re: Guideline 1 in The evaluation techniques document

From: Al Gilman <asgilman@iamdigex.net>
Date: Fri, 25 Jun 1999 10:18:36 -0400
Message-Id: <199906251412.KAA215604@relay.interim.iamworld.net>
To: w3c-wai-er-ig@w3.org
At 05:26 PM 6/24/99 -0400, Leonard R. Kasday wrote:
>At 04:22 PM 6/24/99 -0400, Nir Dagan wrote:

ND::
>>Generally null is not white space but the specs say that leading and
>>trailing white space in CDATA attribute values can be egnored by user
>>agents. E.g., "myval" may be treated as " myval "

AG::
I believe that the word used is "may," not "can."  I believe that what the
editors of the HTML specification were trying to get across was how to work
around a fact of current implementation.  Something like:

"Although a strict SGML interpretation of the CDATA type would indicate that 
' myval ' and 'myval' are distinguished values, users of HTML should be
aware that implementations may treat ' myval ' as if it were 'myval'.

Note that this situation is not symmetrical.  Implementations will likely
strip, but not likely add, leading or trailing whitespace in extracting
attribute values.

LK::
>
>In addition, http://www.w3.org/TR/REC-html40/types.html#h-6.2 states that
>
>"Authors should not declare attribute values with leading or trailing white
>space. "
>
>Seems to me that rules out " " or am I reading this wrong?  It looks like "
>" has both leading and trailing white space in fact.

AG::

I think you have to distinguish "leading whitespace" from "initial
whitespace" to parse this situation correctly.

In other words, leading whitespace is whitespace preceding the first
non-whitespace character, and trailing whitespace is whitespace occurring
after that last non-whitespace character.  Neither are present in " ",
although it meets the criteria both for initial and final whitespace.

>
>Len

Al

>
>At 04:22 PM 6/24/99 -0400, Nir Dagan wrote:
>>Generally null is not white space but the specs say that leading and
>>trailing white space in CDATA attribute values can be egnored by user
>>agents. E.g., "myval" may be treated as " myval "
>>Regards,
>>
>>Nir Dagan
>>
>>http://www.nirdagan.com
>>mailto:nir@nirdagan.com
>>
>>"There is nothing quite so practical as a good theory." 
>>-- A. Einstein
>>
>>On Thu, 24 Jun 1999, Al Gilman wrote:
>>
>>> At 11:56 AM 6/24/99 +0300, Nir Dagan wrote:
>>> >I realy do not understand the idea behind:
>>> >
>>> >Not allowed - NULL ALT value (ALT="")
>>> >Allowed - ALT value of 1 or more spaces (ALT=" ")
>>> >
>>> >Both from a semantic/logical point of view and HTML specification 
>>> >these are quite the same thing.
>>> 
>>> Not quite.  You are ignoring the way logic depends on lexical analysis or
>>> the recognition of word boundaries.  "Lay out" is a verb while "layout" is
>>> a noun.  The logic depends on the lexing.  Whitespace is not guaranteed to
>>> be logically without effect.  Null is not whitespace, space is.  There are
>>> enough situations where this introduces a semantic difference.
>>> 
>>> In the HTML specification it merely warns that some user agents may ignore
>>> whitespace in certain circumstances.  I do not believe that you will find
>>> this carried forward in either the work on XML normalisation nor in the
>>> Internet-Draft from DRUMS updating RFC 822.  What I am saying is that the
>>> best thinking on this issue is that a null string and linear whitespace
are

>>> logically different, a distinction that must be preserved.
>>> 
>>> Al
>>> 
>>> >
>>> >My major reservation with this guideline is that there may be out there 
>>> >many people who took the effort to write accessible pages with alt=""
>>> >where appropriate, and now we tell them to revise their pages, without
>>> >any reason whatsoever.
>>> >
>>> >Regards,
>>> >Nir Dagan
>>> >
>>> >http://www.nirdagan.com
>>> >mailto:nir@nirdagan.com
>>> >tel:+972-2-588-3143
>>> >
>>> >"There is nothing quite so practical as a good theory."
>>> >-- A. Einstein
>>> > 
>>> 
>>
>>
>>
>-------
>Leonard R. Kasday, Ph.D.
>Universal Design Engineer, Institute on Disabilities/UAP, and
>Adjunct Professor, Electrical Engineering
>Temple University
>
>Ritter Hall Annex, Room 423, Philadelphia, PA 19122
>kasday@acm.org        
>(215} 204-2247 (voice)
>(800) 750-7428 (TTY)
> 
Received on Friday, 25 June 1999 10:12:54 GMT

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