Re: A7: CDATA, RCDATA, TEMP marked sections?
On Thu, 03 Oct 96 18:23:07 CDT, Michael Sperberg-McQueen
>On 9 October 1996, the ERB will vote to decide the following question.
>A non-binding preliminary vote indicates the question needs further
>discussion in the work group.
>A.7 Should XML have CDATA, RCDATA, and TEMP marked sections or not?
A number of thoughtful questions have been raised in this thread regarding the
motivation for the CDATA design. I'll try to answer them.
1. The ugly (that is to say, distinctive) syntax.
A design principle of SGML is that different kinds of information have different
syntaxes. Processing instructions are different from comments are different from
elements are different from specially-parsed data. The syntactic distinctions
emphasize the semantic ones to remind the user that different rules are in
effect and different behaviors will apply. The syntactic differences also allow
SGML to avoid impinging on the user's name space, as it would have to do if,
say, comments were element types.
2. Why a CDATA element is terminated by any end-tag.
Because we goofed.
An original objective of SGML, believe it or not, was to support DTD-less
parsing of an instance. Obviously, we blew it in the final product by not making
CDATA element types, etc., optional. (In fact, we had many more options at one
time, but were pressured into "simplifying" things. SHORTTAG was a combination
of what started as several independent features.)
<digress>Multi-year projects in a highly political arena with changing personnel
contributes to a loss of focus. WG8 has gotten much, much better at managing the
standards process since then. The review process for SGML97 started out by
agreeing on objectives and procedural rules and writing them down. XML has
wisely done the same.</digress>
The error was compounded by the fact that we couldn't agree (or occasionally
forgot whether we agreed) whether we could expect a dumb parser to keep a stack.
We'll fix this bug in SGML97.
Charles F. Goldfarb * Information Management Consulting * +1(408)867-5553
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