Re: questions about entities and entity declarations

On Tue, 24 Sep 96 11:41:47 CDT, Michael Sperberg-McQueen
<U35395@UICVM.CC.UIC.EDU> wrote:

>This logic eludes me completely.  The premise is false, since meaningful
>existence can be defined by an application in its own terms; an
>application doesn't need our permission to assign meaning to a text
>entity.  And even if the premise were true, the conclusion doesn't
>follow.  I might wish to point to an external entity which contains
>an alternative rendition text for the element, which has a fragment
>of an SGML document which can meaningfully be substituted for the
>content of the element.

>Where is the problem?

The problem is that you have subverted the chief purpose of SGML, which is to
preserve the "true" information content. An application is forbidden to do
anything that would affect the parsing of the document, otherwise there would be
no portability because there would be no guarantee that all applications would
see the identical parsed input.

SGML text entities are part of the true information; they are parsed *in
context*. No other entities are parsed in context, except for the SGML document
entity in which everything begins (and which establishes the context in the
first place).

An application can, of course, treat an attribute value as a replacement for the
*parsed data* that the parser found in the element's content, but that only
affects the output of the application. Such an attribute should not be labeled
an "SGML text entity" because that label identifies text that is parsed *in
content*. The attribute should be a CDATA (with SGML notation) or SUBDOC entity,
as those are parsed *out of context* at the request of the application. (See my
postings on entities for more details.)

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