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Re: Optional features considered harmful

From: Charles F. Goldfarb <Charles@SGMLsource.com>
Date: Fri, 25 Oct 1996 03:37:06 GMT
To: James Clark <jjc@jclark.com>
Cc: Michael Sperberg-McQueen <U35395@UICVM.UIC.EDU>, W3C SGML Working Group <w3c-sgml-wg@w3.org>
Message-ID: <32823225.28264502@mail.alink.net>
On Thu, 24 Oct 1996 21:32:46 +0000, James Clark <jjc@jclark.com> wrote:

>At 15:23 24/10/96 CDT, Michael Sperberg-McQueen wrote:
>>>It would be easier to make this work if we disallowed references to
>>>external text entities in attribute values, but hopefully people can
>>>live without those.
>>Er, I'm sorry if I'm missing something, but doesn't clause
>>(p. 335 of Handbook) restrict ENTITY/ENTITIES attributes to
>>data and SUBDOC entities?  I.e. isn't your conditional already met?
>I'm talking about *references*; for example,
>  <!entity e system "e.sgm">
>  <foo a1="&e;">

Maybe that's the problem.

In order for an external SGML entity to be ignored safely by the parser, it has
to be a document entity (or subdoc, which for our purposes is the same thing).
Therefore, if we restrict external SGML/XML entities to being referenced from
attribute values, we can have reusable objects (as Eliot has pointed out) and we
don't have to redefine the meaning of an entity reference.

<p>As is shown in the following text:<quoteref entity=ent1> ...</p>

Of course, "quoteref" is really a typed hyperlink, as is any "entity reference"
that a parser can safely ignore.

My conclusion: drop the optional entity references. We'll get them back in a
robust and fully conforming form when we add hyperlinking.
Charles F. Goldfarb * Information Management Consulting * +1(408)867-5553
           13075 Paramount Drive * Saratoga CA 95070 * USA
  International Standards Editor * ISO 8879 SGML * ISO/IEC 10744 HyTime
 Prentice-Hall Series Editor * CFG Series on Open Information Management
Received on Thursday, 24 October 1996 23:37:01 UTC

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