Questions on DCD

[Dean Roddey]

"One downside is that the DTD can't validate the constraints formulation
(unless you have a custom constraint that checks constraints, but that
is pretty circular).  Schema authors are a fairly rarified bunch, so I
wouldn't be enormously concerned about a few extra keystrokes (we will
program our editors to do it for us, or when we finally get useful
DTD-aware editors, it would auto-complete the elements for us).  I would
think the parser authors would bypass DOM creation so I don't see DOM
space as being a huge issue."

But the same verbosity is imposed upon the user of the validation scheme
as well, right?

As for sciping the DOM creation, I don't think you could, could you?
Because of the open ended nature of the validation mechanism, if it was
done as an element and its subcontent, there could be a lot of information
in there that only the target validation function would understand how to
make use of. How would you get that information to the function if you
didn't either use my scheme of giving him an open ended string that he
can parse, or building some known format (i.e. a DOM node) to pass to it?

I dunno. In some ways you win and lose either way. Given the very open
endedness of the scheme, I'd prefer the single formula style. But that's
just my opinion, and I'm looking at it from a user's point of view not
a machine's. From a machine's point of view, the element scheme would
probably be more useful.

"One thing that we are doing is adding an documentation fragments to that
we can process DCD and generate HTMLHelp manuals for the schemas we are
developing.  Doing constraints as XML elements, would give us somewhere
to explain the constraints."

That's a good point.

----------------------------------------
Dean Roddey
Software Weenie
IBM Center for Java Technology - Silicon Valley
roddey at us.ibm.com

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