From: David Alan Black <dblack@...>
Date: 2001-12-16T01:55:46+09:00
Subject: [ruby-talk:28629] Re: DTD Parsers in Ruby?

Hello --

On Sun, 16 Dec 2001, Sean Russell wrote:

> Technically, aren't all XML documents also well-formed SGML documents?
> This can't be said of DTDs.  So I'd say that XML isn't a hack, but a
> dailect.  DTDs are a hack... you can't parse a DTD with code that parses
> SGML.

I'm not sure how the word "hack" got into the picture here, but
anyway....  A DTD is to the body of an SGML document (the "document
instance") as, say, a regular expression is to a string.  Also, the
DTD is part of the SGML document, by reference and/or by physically
being included.  So in SGML, I don't think the idea of parsing a DTD
as if it *were* an SGML document (in which case it would have its own
DTD, and so on...)  has any currency.  Or maybe that's why someone
decided to create XML :-)

> > Special processing, yes, but not inordinately complex, I think, in
> > relation to the payoff (validation).  (Easy for me to say, since I've
> > written about 10 lines of a processor.)  Also, at least in the case of
> > SGML, it's not really "additional", since every SGML document conforms
> > to a DTD (i.e., that's what the whole thing is about).
>
> I wasn't saying that validation is bad; I was making the case that there
> are better ways to support validation, such as XMLSchema, which uses the
> same syntax as the documents which it describes, and therefore doesn't
> require any special parsing code.
>
> Ob-Ruby: this is even more of an issue in Ruby, where the parsers are
> small.  Requiring an extra parser to support DTDs can easily add 50% to
> your codebase.

Well, we'll have to agree to disagree about the "extra" part :-)  And
before I say anything like, "But people who are looking at XML support
in Ruby aren't going to want to hear language-specific reasons like
that," I'd better do a little more work on my vaporware parser :-)


David

-- 
David Alan Black
home: dblack@candle.superlink.net
work: blackdav@shu.edu
Web:  http://pirate.shu.edu/~blackdav