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Re: B.10 Empty elements?

From: <lee@sq.com>
Date: Mon, 14 Oct 96 20:39:57 EDT
Message-Id: <9610150039.AA24259@sqrex.sq.com>
To: cbullard@HiWAAY.net
Cc: w3c-sgml-wg@w3.org
Len --

the problem with needing lookahead at all (never mind if it's a page
or 200 pages) is that the parser has to be more sophisticated.
To the Jameses of this world :-), that might not seem like a big deal,
but to the Dirty Perl Hackers it might mean somewhat more, and to the
Hordes of Mediocre C Programmers, it means a lot more.

this is why I am championing <@BR>.

>> If empty elements were marked syntactically, e.g.
>> <@PGBRK>
>> then there would be no problem.
>> This can be done by allowind @ as a name start character, and then
>> saying that in XML, empty elements have names starting with @.
>> If SGML could be augmented to allow a different open tag delimiter for
>> EMPTY elements, it could use <@, and the entire problem would vanish.

>That appears to me to be a solution.  Doesn't this break compatibility 
>with SGML?  Is it something that SGML 97 could quickly address?
> Charles?

I am not Charles :-), but no, adding @ as a name start character is
legal SGML, and although I don't know if many SGML applications allow it
today, they'll all have to be modified to deal with DTD-less XML anyway,
or (more likely) use an external translator.

Using the different open tag delimiter would need changes to SGML -- the
advantage would be twofold:
(1) you could say
    <!Element BR - O EMPTY>
    <!AttList BR
        jointype (clean|ragged|other) #IMPLIED
rather than using @ in the element name, and, more importantly,

(2) the SGML parser would then understand the convention as well as the
    XML programs.  But it would work as an XML application convention quite
    well without that.

Received on Monday, 14 October 1996 20:40:29 UTC

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