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RE: [xml-dev] Boolean attributes in XHTML/HTML5

We lost inclusions too and while I occasionally miss them, I can cope.
While cleaning out my studio last weekend, I found the print copies of
the original IADS DTD and the source code for ARC SGML (a markup museum
should have that).  For the young ones, ARC SGML is the parent of SGMLS,
the first free SGML parser I am aware of.  Stories there too but not
mine to tell.

I heard a lot of interesting fables about the pre-SGML HTML days.  From
those and the crossing-the-chasm days on comp-text-sgml that I remember,
I think you are right and the stories that TBL intended to do RTF are

Like all plans, time, test results and the occasional falling apple led
in the right direction.


-----Original Message-----
From: Peter Flynn [mailto:peter@silmaril.ie] 
Sent: Tuesday, February 28, 2012 4:06 PM
To: xml-dev@lists.xml.org
Subject: Re: [xml-dev] Boolean attributes in XHTML/HTML5

On 10/02/12 14:18, David Carlisle wrote:
> On 10/02/2012 14:02, Len Bullard wrote:
>> Which doesn't answer the question why they didn't choose
> I wasn't involved but presumably because that would lead people to
> that the attribute value mattered and that disabled="no" meant
> different from disabled="yes". The point about boolean attributes as
> interpreted by browsers is that they are true if they are there (with
> any value) and false if they are not there.

 From memory, assisted by a trawl of the IETF HTML-WG at 
https://listserv.heanet.ie/cgi-bin/wa?A0=HTML-WG, there was no decision 
at all.

I believe the pre-HTML2 code samples (TBL?) originally used <option 
selected> and <input type=radio checked> because it wasn't actually 
meant to undergo a formal SGML validation, so the question of what 
"checked" and "selected" implied (as attributes) was not under 

When we cast HTML2 as a DTD, the values had to be declared as 
*something*, and creating an attribute called after the value you wanted

to minimise it to probably seemed like a good idea at the time. I don't 
recall it ever being questioned.

> so in html you have <foo> and <foo disabled> as markup, in XML where
> need to supply a value, disabled="disabled" is valid for legacy
> disabled="" is valid because that's what people thought the syntax was
> anyway and anything else including disabled="no" acts the same way as
> disabled="" but is classed as non conforming (which only matters to
> validators not to browsers)

There are lots of other attribute minimisations that could have been 
used if formal validation had been on the cards. The following is valid 
SGML, for example:

<!doctype html public "-//IETF//DTD HTML 2.0 Strict//EN">
<li><input radio>A
<li><input radio checked>B
<li><input radio>C
<input submit>

But as most browser writers didn't actually know any SGML, the question 
never arose.



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