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Re: ERB decision, 31 October 1996

From: David G. Durand <dgd@cs.bu.edu>
Date: Tue, 5 Nov 1996 11:18:33 -0400
Message-Id: <v02130501aea509015951@[128.148.157.46]>
To: W3C SGML Working Group <w3c-sgml-wg@w3.org>
At 1:24 AM 11/5/96, Charles F. Goldfarb wrote:
>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.

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

A syntaxctic entity refrence, as the discussion makes clear.

>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.)

As far as the text says, no. What is not forbidden is permitted. Therefore
the requirement is wisely not made!

> 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.)

This makes some sense in a DP environment with fixed files for entities,
but not on the web, as I have argued before.

>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.)

Entity attributes are not _included_ in the document however, so the
functionality of a normal entity reference is not provided.

>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.

They can create such systems on top of XML if it is useful. I do not expect
that anyone will be soe moved. We should defnitely not attempt the
foolishness of wagging our fingers at users and saying "naughty, naughty,
you used variable replacement text!" XML requirements are requirements for
the parser to enforce conditions. Ipso facto, we cannot make requirements
that we cannot enforce.

   -- David


RE delenda est.
I am not a number. I am an undefined character.
_________________________________________
David Durand              dgd@cs.bu.edu  \  david@dynamicDiagrams.com
Boston University Computer Science        \  Sr. Analyst
http://www.cs.bu.edu/students/grads/dgd/   \  Dynamic Diagrams
--------------------------------------------\  http://dynamicDiagrams.com/
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Received on Tuesday, 5 November 1996 11:08:54 EST

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