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Re: ERB decision, 31 October 1996

From: Charles F. Goldfarb <Charles@SGMLsource.com>
Date: Tue, 05 Nov 1996 05:24:24 GMT
To: Michael Sperberg-McQueen <U35395@UICVM.UIC.EDU>
Cc: W3C SGML Working Group <w3c-sgml-wg@w3.org>
Message-ID: <328acefe.18449027@mail.alink.net>
On Thu, 31 Oct 96 13:01:34 CST, Michael Sperberg-McQueen <U35395@UICVM.UIC.EDU>
wrote:

>    a reference to an external text entity is a signal to an XML
>    processor that the entity's contents are to be included at the
>    point of the reference.  For purposes of *validation*, an XML
>    processor must fetch and read the external text entity at the
>    point of reference; for other purposes, processor behavior is
>    not constrained.

I have some questions about this:

1. Is a "reference to an external text entity" a syntactic entity reference, a
general entity name attribute value, or both?

2. Will XML require that a syntactic entity reference to an external text entity
yield the identical text every time it is resolved? This rule is a requirement
for 8879 conformance. (It is not an issue of validation, nor is it related to
the time or context of parsing.)

 A fundamental principle of SGML (perhaps *the* fundamental principle) is that
parsing the *SGML text* of a document produces the same data, every single time.
Without that principle, SGML documents aren't portable and reusable. (Data
entities aren't affected by this rule, since they aren't parsed in context.)

The SGML user can distinguish constant text from variable data by the syntax.
Syntactic entity references must always resolve to the same text; entity
attributes need not. (This has nothing to do with validation.) 

Even though parsers cannot enforce this distinction, users are entitled to
express it in their markup, as it could be meaningful for document management
applications.
--
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 Tuesday, 5 November 1996 00:24:42 EST

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