>> Parsed entities are pretty much dying as XML Schema replaces DTDs.
I think you'll find them alive and kicking in many places. Reports
of the death of DTDs are greatly exaggerated.
Uhm. I agree that schemas are taking longer to find their way in than
might have been expected, partly becuase they're a syntax only a
database expert or computer science geek could love. (Though frankly the
DTD syntax is also pretty hideous.)
However, entities are definitely on the way out. The problem is that
they really aren't all that useful unless there's a fragment that will
appear in a huge number of instances of this kind of document, and even
then they're only a significant advantage when producing the document by
hand; it is a significant pain for software to recognize that the
opportunity exists to take advantage of a parsed entity, and there
usually isn't much to be gained by doing so.
Entities had value when most docs were produced by humans pounding on
raw XML text; they really aren't useful for docs produced by smarter
editors. Most of the things you might still want to use them for can be
handled better by an appropriate tool -- an editor that lets you see and
enter the actual characters rather than their named equivalents, for
example, or a syntax that's actually defined in the document rather than
in a non-tag-language secondary file. Among other things, that permits
different documents to reference different resource rather than having
only a single set, hard-wired into the DTD, that they can name.
XInclude/XLink were supposed to take over that role.
Oooh look, flying pigs :-)
I did put it in the imperfect tense... Part of the problem is that we're
finding that the need for a portable syntax for documents referencing
other documents isn't as universal as we expected. Or at least isn't so
right now.
If we'd designed XML completely before releasing it to the public, we
would have started with the infoset (including namespaces and schemas
and includes and links), then designed the syntax and APIs from that,
Instead the W3C started with the syntax and a known-inadequate schema
language (DTDs), and has build everything out from there. The upside is
that folks had a chance to start using XML much earlier, and we've
gotten some benefit from seeing which directions everyone has gone with
it. The downside is that there have been some warts and hiccups and
direction changes along the way, and tools have not always been quick to
catch up -- and even when they have, folks who have working solutions
using the old stopgaps are often reluctant to make the effort to move
over. Which leaves all of us with the job of supporting multiple ways of
doing things and trying to gently push folks toward the ones that will
make their life -- and ours -- easier in the long run.
Oh well. The cutting edge usually has a few nicks in it.
--
() ASCII Ribbon Campaign | Joe Kesselman
/\ Stamp out HTML e-mail! | System architexture and kinetic poetry