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RE: [xml-dev] Boolean attributes in XHTML/HTML5
- From: "Len Bullard" <Len.Bullard@ses-i.com>
- To: "Peter Flynn" <peter@silmaril.ie>,<xml-dev@lists.xml.org>
- Date: Tue, 28 Feb 2012 16:17:18 -0600
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
also.
Like all plans, time, test results and the occasional falling apple led
in the right direction.
len
-----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
disabled="yes".
>
> I wasn't involved but presumably because that would lead people to
think
> that the attribute value mattered and that disabled="no" meant
something
> 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
consideration.
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
you
> need to supply a value, disabled="disabled" is valid for legacy
reasons,
> 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">
<title>Test</title>
<form>
<ul>
<li><input radio>A
<li><input radio checked>B
<li><input radio>C
</ul>
<input submit>
</form>
But as most browser writers didn't actually know any SGML, the question
never arose.
///Peter
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