Re: C.4 Undeclared entities?

[Charles Goldfarb:]

| I hope someone can prove me wrong by rebutting the following
| proposition (formal mathematical proof not required):
| 
| XML without a DTD is no different from HTML extended by the ability to
| "add tags and attributes" just by defining processing for the
| additions in a style sheet (cascading or otherwise).

A well-formed XML document without a DTD describes a logical tree of
arbitrary depth.  HTML does not, unless you overload the DIV tag in
ways that are horrible to contemplate.  This is a difference.

[Tim Bray:]

| Whether in fact there is much, other than display, that you can
| usefully do to an SGML document without having a DTD, is something
| that only the market will decide.

Some of us have already decided.

I put documents totalling hundreds of thousands of pages of SGML
online using a tool in which the DTD was optional except for EMPTY
elements and entity declarations.  The result supported every
operation that I wanted to perform on those documents, including a
variety of rather complex structural queries.  While there are no
doubt many applications for which such a system would be inadequate, I
found that SGML without a DTD provided me with everything that I
wanted SGML to do as a publishing medium, with the single exception of
validation.  A lot of other DynaText/DynaWeb users found this out,
too.  I predict that a lot of XML users will come to the same
conclusion.

Jon