DTD Notation - Annex K

From owner-xml-dev@ic.ac.uk Wed Apr  1 12:32:29 1998
Date: Wed, 01 Apr 1998 12:20:58 -0600
To: xml-dev@ic.ac.uk
From: "W. Eliot Kimber" <eliot@isogen.com>
Subject: Re: Proposal for src files

[See as of April 20, 1998: http://www.ornl.gov/sgml/wg8/document/1963.htm.]

At 09:22 AM 4/1/98, Peter Murray-Rust wrote:
>Is it possible to combine these two so that we express a DTD
>in a standard XML notation?

Technical note: at the recent NCITS (nee ANSI) meeting, the U.S. delegation to WG4 developed a proposed amendment to the SGML standard that codifies the idea of DOCTYPE declaration components that are not in DTD syntax.

The idea is very simple: allow "parameter data entities", e.g.:

<!NOTATION MySchemaLanguage 
  PUBLIC "-//ME//NOTATION My Schema Language//EN" 
<!ENTITY % my-declarations 
  SYSTEM "mydecl.schema" 
  NDATA MySchemaLanguage 

The only requirement is that the document allow omitted DTD declarations. If the parser understands the notation of the parameter data entity, it can use it to do SGML validation to the degree it can construct the prolog portion of the document grove from the entity. If it doesn't understand the notation then the normal implied declaration rules apply. Any validation services over and above SGML validation must be clearly labeled as such (i.e., consistent with SGML's current distinction between validation errors and application warnings).

Because the external DTD subset is really a parameter entity, you can make the whole external subset a parameter data entity:

<!DOCTYPE MyDoc SYSTEM "myschema.schema" NDATA MySchemaLanguage [
  <!NOTATION MySchemaLanguage 
    PUBLIC "-//ME//NOTATION My Schema Language//EN"  

Note that the internal subset is unchanged: you must use normal DTD syntax within the DTD subset.

If approved by ISO, this ammendment would make SGML's official policy on schemas "use any syntax you want, we don't care". In particular, we have no plans or desire to define alternative syntaxes for DTD representation within ISO 8879. This does not, of course, preclude separate schema standardization efforts within NCITS or ISO (or anywhere else).

So far this proposal seems to be non-controversial.

<Address HyTime=bibloc>
W. Eliot Kimber, Senior Consulting SGML Engineer
Highland Consulting, a division of ISOGEN International Corp.
2200 N. Lamar St., Suite 230, Dallas, TX 95202.  214.953.0004

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