W3C home > Mailing lists > Public > w3c-sgml-wg@w3.org > December 1996

Re: simplifying comments in SGML '97

From: Paul Grosso <paul@arbortext.com>
Date: Sun, 15 Dec 96 13:05:36 CST
Message-Id: <9612151905.AA12073@atiaus.arbortext.com>
To: w3c-sgml-wg@w3.org
> From: Michael Sperberg-McQueen <U35395@UICVM.UIC.EDU>
> 
> The XML spec of 14 November defines as a 'comment' what in 8879 is
> called a 'comment declaration' -- to reduce confusion, in what
> follows I am going to try to use the 8879 terminology, not the XML
> terminology.
> 
> The current version of the XML spec differs from 8879 in various ways:
> 
>   (a) XML allows comments *only* in comment declarations; 8879
>       allows them in other markup declarations as well (though not
>       in all locations)
>   (b) XML allows exactly one comment in a comment declaration;
>       8879 allows zero or more
>   (c) XML defines two delimiters '<!--' and '-->' which bound the
>       construct in question; 8879 sees three delimiter roles involved
>       here, and allows white space in some locations:  XML '<!--'
>       corresponds to 'mdo, com' in 8879 (this is split across
>       productions 91 and 92, pp. 391 of the Handbook) and XML
>       '-->' corresponds to 'com, s*, mdc' (again, productions 91-92)
> 
> N.B. I think this list is complete but may be wrong.
> 
> The main perceived problem with the XML spec is that the comment itself
> is barred not only from containing '-->' (its closing delimiter) but '--'. 

While I'll admit to being somewhat inclined to use mdashes in my 
writing--and have occasionally been caught doing so in an SGML
comment declaration--I do not see the benefits of being able to
put "--" in a comment as being so great as to warrant doing something
that is either particular complicated or different from what SGML
parsers do today.  When people start getting too concerned about
what they can put into comments, they are probably putting too 
much into comments, and should probably consider creating elements
in their DTD to hold the supposed "comments."

I think each time we propose changing XML's syntax from that which
is the syntax of the SGML in common usage for the last 10 years, we
need to ask if the preceived benefits are worth it.  In this case,
I prefer to leave XML comments as defined in the XML draft.
Received on Sunday, 15 December 1996 15:22:15 EST

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