Len Bullard cbullard at
Wed Mar 24 04:08:06 GMT 1999

Marcelo Cantos wrote:
> Of course, none of the above discourse will eliminate the need for
> discussion on what, exactly, is needed and how that need is to be
> satisfied.  As one colleague astutely pointed out to me, I am really
> transforming the issue from "real validation" to "sufficient
> validation".  It would be a mistake, however, to conclude that this is
> a trivial transformation in the statement of the problem.  It diverts
> the emphasis of the search markedly away from completeness and towards
> practicality and useability (of course, completeness remains
> desirable, it merely ceases to be a central goal).

Not in disagreement.  Still, DTDs play a role in expressing constraints 
that in some way, must be implementable and to some degree must be 
validated for a particular piece of content.  Here is a different 
kind of schema from the VRML language.  How would any/all of the 
DTDs/schemas proposed for XML be used to define this?  Which if 
any are better?

Transform {
  eventIn  MFNode addChildren
  eventIn  MFNode removeChildren
  exposedField SFVec3f  center 0 0 0
  exposedField MFNode children [ ]
  exposedField SFRotation 0 0 0 1 0
  exposedField SFVec3f  scale 1 1 1 
  exposedField SFRotation scaleOrientation 0 0 1 0
  exposedField SFVec3f translation 0 0 0
  field SFVec3f bboxCenter 0 0 0
  field SFVec3f bboxSize -1 -1 -1


It isn't a trick question.  Serious people are currently evaluating 
the suitability of XML for this.  In this form, the declaration is 
quite compact.  Right now, without datatypes and without event models, 
this *simple* node may be more than XML can describe.

Any takers?

len bullard

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