Conal, in your reply to Paul, you say ....
>Message-ID: red-39-msg951208205007MTP[01.51.00]000000db-34209
>
>Paul,
>
[text delete]
>Given the inevitability of imperfect presentation of ideal models on
>computers, one must decide what to present, so as to optimize the
>user's experience. This question is a deep one, and is as much a
>question of perceptual psychology as one of computer science or
>engineering. Our own implementation is designed to go back in time to
>set the system back on the correct path, based on the accurate though
>somewhat belated knowledge that an event did occur, when it occurred,
>and what values were associated with the occurrence. I suspect that
>maintaining a few low orders of spatial continuity will be
>perceptually desirable, even though doing so slightly prolongs the time
>interval during which the user experiences an inaccurate result. We
>will need to do more experimentation and user testing before concluding
>what approach to recommend.
>
>| What you are proposing would be useful for flexible dead-reckoning.
>| But what if you received a behavior which operates over a time
>| interval whose beginning has alesady passed and which affects what
>| the user sees (in the past)? Rollback is just one solution to the
>| synchronization problem, and not necessarily the most desirable one.
>|
If I understand your model correctly then the problem Paul is trying to get
at (I think) is that your approach of hiding inconsistencies during a given
time interval and then going back and repsiring those inconsistencies will
only work in a closed system.
Your model seems to propose some notion of rollback, rollback only works in
a closed system where the effects of the incorrect assumptions (the
inconsistencies) are contained or bounded, Usually this is done in within
the scope of a transaction.
A shared VRML world is not a closed system, it exposes its internal state
to the user and to the rest of the world users via the network. As such, it
becomes very difficult to rollback - in your text I think you suggest that
its possible to rollback a local world view without the user becoming too
confused. I don't agree with that and I think you are making an implicit
assumption that the time periods during which inconsistencies occour will
be short. In a shared 3d world with users spesad out across the network you
will end up with long periods of inconsistency, and with different
inconsistencies - distributed rollback is a difficult problem.
If I understood Pauls original comment - the issue is that your functional
model hides the notion of time (or abstracts away from it). This makes it
very difficult to deal with distributed models were each end point has a
different view of that time.
rodger