The current model is, web browsers downloads the entire file and passes
it off to an external application, and that's that. Now, certain
browsers, like Mosaic for X (possibly Mac - I know MacWeb replies to some
AppleEvents) can be controlled to fetch another document, but feeding that
back to the external browser already open is currently unsupported. I
imagine being able to do things like open up a scene with a teapot and
table and chairs, where those objects are possibly-cached-or-separately-
obtainable, is something that should wait until after the 1.0 version of
VRML, until we have Web browsers than can handle VRML internally. Or
maybe this issue doesn't have to hinge on VRML at all.
Brian