One is URN's versus URL's. URN's are a location independant naming scheme,
the URI group won't tackle what is wanted here because it doesnt even come
close to what they are trying to tackle. (I wrote one of the contenders for
URN spec).
Another is caching, we want to make sure that we are able to use a local
object if we have it cached, this can apply whether we have the copy on CD
or just cached from the last time we accessed it, and is independant of
whether we use URL's or URN's to access the object. Note that one neat
feature of using HTTP and Caching, is that we can have a CDRom with a bunch
of cached objects, and still be able to retrieve later versions by HTTP
since it can check for whether the object has been changed since the date
on the version cached.
The third is defaults, i.e. how to I display a generic teapot while I'm
waiting for the specific teapot. This should be orthogonal, for example I
might really want http://obscure.com/realcoolteapot.wrl, but would accept
http://vrml.com/generic/teapot.wrl. I think its important that the default
should also be a URL (or URN), just one more likely to be cached.
Here is a suggestion that might allow us to handle this reasonably,
although I'm much more interested in successfully seperating out the three
concepts, than in using any specific syntax for it.
WWWInline {
name "http://obscure.com/realcoolteapot.wrl"
default "http://vrml.org/generic/fancyteapot.wrl"
default "http://vrml.org/generic/teapot.wrl"
hint CACHE
}
Note that the multiple defaults would allow us to successively look for
less acceptable, but more likely to be cached, objects.
Unfortunately it would violate the syntax rule about fields not being ordered.
- Mitra
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