Re: A17: keep or drop entities?

On Thu, 10 Oct 1996 10:12:13 -0400, "Eve L. Maler" <elm@arbortext.com> wrote:

>At 04:49 AM 10/10/96 GMT, Charles F. Goldfarb wrote:
>>Actually, Tim, I was supporting your position. The keyword SDATA in the ISO
>>character entity set is unnecessary because the replacement text is a symbolic
>>string. (My original intention was that a system would use an equivalent entity
>>set in which the replacement text was real system data.)
>The [xxxxxx] replacement text "templates" have been widely implemented 
>to produce the desired glyphs.  But this doesn't mean they're not system
>data, does it?  It's still essentially a "processing instruction that
>returns data" (clause 8).  Regular internal text entities aren't 
>supposed to have this property.

Eve has made a very sensible observation, so let me explain my reasoning.

There are two principal purposes for labeling SDATA and PI:

1. To make it easy to locate and revise or remove system-specific information.
This, of course, enhances document portability and reuse by containing system

2. To prevent generated text from being parsed in context with the SGML
document. This enhances portability and reuse by assuring that all applications
will "see" the same data.

The symbolic replacement text in the ISO 8879 character entity sets don't
present a problem on either of those counts. They are not system-dependent and
they parse identically in all environments. That is because the generation of
system-specific data takes place in the *result* document; it is never seen by
the parser. In pernicious SDATA, the entity text is system-specific and
therefore needs to be labeled.

In the context of creating a simplified subset of SGML that had to be usable in
a wide range of system environments, it seemed reasonable to eliminate SDATA
entities. In order to allow the ISO character entity sets to be used with the
SGML subset, I proposed removing the SDATA keyword from them.
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