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delimiters (Re: A7: CDATA, RCDATA, TEMP marked sections?)



On Thu, 10 Oct 1996 lee@sq.com wrote:

> But I expect that XML will have SGML's weird multiple syntaxes... :-(

Is the programming language world really so simple? What about C++?

It has three comment delimiters:

	// for C++
	/* */ from C
	# (at beginnning of line) from cpp

It has different delimiters for blocks ( {} ) and statements ( ; )
and function calls ( () ). 

People complain that LISP is difficult to read because it only has one
delimiter for comments and one for function calls. The reasons for C++'s
multiple comments delimiters might be artifacts of its implementation
history, but C++ syntax is more popular than LISP syntax, as Java proves.

One very good reason for tag delimiters and comment delimiters to be
different is that if they are different non-SGML-aware text tools can play
with them.  E.g. off-the-shelf text editors can display markup in
different colors, if they they can detect the markup easily.  This is
something we use a real lot here, and we even make sure our SGML documents
are marked up so that the simple detection mechanism based on delimiters
with no context will be reliable: e.g. < and & always must be done by
entity references, and CDATA content models are deprecated. (I guess it
means we already try to make our in-process documents more like XML
already.)

While it might be good to have a comment declaration like you suggested in
SGML, I think it would be a terrible idea in XML: anything that requires 
context or previous declarations to parse should be viewed as suspect
and complicating.

But even in SGML, you could declare an architectural form or fixed attribute 
for an element that labels it as having the nature of a comment.


Rick Jelliffe            http://www.allette.com.au/allette/ricko
                         email: ricko@allette.com.au
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