Message-Id: <email@example.com> Date: Sun, 22 Sep 1996 17:37:30 -0500 To: Foteos Macrides <MACRIDES@SCI.WFBR.EDU> From: firstname.lastname@example.org (Murray Altheim) Subject: Re: Simple(?) question on obscure comments detail Cc: email@example.com Foteos Macrides <MACRIDES@SCI.WFBR.EDU> writes: >firstname.lastname@example.org (Murray Altheim) wrote: >>[...] An SGML markup declaration >>begins with a "markup declaration open" (MDO), which in the reference >>concrete (ie., default) syntax is defined as: >> >> <! >> >>Following immediately after this (no whitespace) is the declaration type. >>There are 13 types of markup declarations in SGML, but only one is allowed >>in the document instance: the comment declaration. > > Perhaps this is a problem of me not yet being clear on the precise >meanings of SMGL terms, but isn't it now two for HTML: > > <!-- > >and: > <!DOCTYPE You're fine on the terms. I wrote: >Following immediately after this (no whitespace) is the declaration type. >There are 13 types of markup declarations in SGML, but only one is allowed >in the document instance: the comment declaration. All others are specific >to the document prologue (SGML declaration, DTD, etc.). [...] You may find both comment and DOCTYPE declarations in an HTML _file_, but the structure of an HTML _document_ includes both the prologue and document instance, so the DOCTYPE is considered part of the prologue. This is one of the interesting parts of SGML: you preface your content with the specification of its markup structure. You could theoretically include the entire DTD in the prologue, rather than just referencing it as a piece of PUBLIC text. You can also include a modified SGML declaration, as is being done for the internationalized HTML DTD that handles the extended character set: BASESET "ISO Registration Number 176//CHARSET ISO/IEC 10646-1:1993 UCS-2 with implementation level 3//ESC 2/5 2/15 4/5" Current HTML-only browsers wouldn't understand modifications to the prologue (most ignore it entirely), but an SGML browser would. Prologue: <!SGML "ISO 8879:1986" ... > (assumed) <!DOCTYPE html PUBLIC "-//IETF//DTD HTML//EN"> Document instance (the "HTML element"): <HTML> [...] </HTML> > Also, wouldn't a real SGML parser handle comments in a DOCTYPE >declaration, but they are presently excluded, or at perhaps "disrecommended", >there for HTML? Such as? <!DOCTYPE html PUBLIC "-//IETF//DTD HTML//EN" -- this is a reference to the HTML 2.0 DTD --> Certainly not recommended (as some browsers might be confused), but valid. Murray ``````````````````````````````````````````````````````````````````````````````` Murray Altheim, Program Manager Spyglass, Inc., Cambridge, Massachusetts email: <mailto:email@example.com> http: <http://www.cambridge.spyglass.com/murray/murray.html> "Give a monkey the tools and he'll eventually build a typewriter."