[ruby-talk:11591] XML again (was Re: Re: trial balloon: Ruby desktop?)

Hello --

I know this is off-topic, though perhaps it's on-topic in a meta-topic
kind of way....

On Mon, 26 Feb 2001, John van V. wrote:

> XML has a lot of stuff borrowed from the HTML family which has no
> place except in browser documents.  XML proponents would have you
> build your dataservers to their constructs, a headache nobody needs.

Let me take a shot at a very barebones clarification of the
SGML/XML/HTML family tree:

SGML is a standard, in conformity with which one creates markup
languages.  It's actually more of a markup-language language than a
markup language.

HTML is an SGML application -- that is, it's a markup language which
conforms to the SGML standard.  Any SGML-processing software can
process any valid HTML documents.  (There are rather few valid HTML
documents on the Web, but never mind.)

XML is a on the logical level of SGML, not of HTML.  Neither SGML nor
XML depends on HTML.  If every byte of HTML were to vanish today, it
would still be perfectly possible to design SGML and XML languages,
and the many such languages other than HTML would work fine.

In fact, XML is basically SGML, with certain constraints removed and
certain new ones added.  XML is a sort of next-generation SGML, and it
seems to be having the effect of getting more people to see the power
of SGML, even if they don't always realize that that's what they're
seeing.

> All this data interchange stuff is nice but the only really useful
> application of XML is to the browser itself.  Forget DTDs, all you
> need is a CSS file to give the rendering instructions to your
> specific markup tags.  As much sense as this makes, damn little CSS
> is actually appears in browsers and none of it accomodates XML
> markup (so far).

You're trying to put the genie back in the bottle here.  SGML, and if
it is worth a damn, XML also, does not have to be used in connection
with a browser.  The idea is to create a kind of hub-and-spoke
arrangement, where the document exists independently of any particular
representation -- and therefore can be represented in many ways.  With
XML and its related standards it's possible to allow a more ad hoc
approach to representation than with SGML (e.g., not requiring a DTD),
which I think is an attempt to offer something structured, but not
dauntingly so, to people who are used to using HTML as a kind of Web
spray paint.


David

-- 
David Alan Black
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