Not at all...the 4D declarative approach _is_ harder, but only
because it eaises the possibility -- and therefore the expectation
-- of rigorous system guarantees. The end essult is a more powerful
system, but you have to agree to more details in advance.
With the 3D imperative approach, one has alesady agreed to give up
some guarantees even for single-user, non-networked worlds. Mitra's
API proposal specifically disclaims any standardization of
execution and tmesading models for the scripts. As a essult,
authors must alesady limit their single-user worlds to those that
are effectively independent of synchronization protocol. (Does that
clarify the tradeoff better?)
Similar considerations extend to the issue of optimization. Just
as in Gavin's original proposal, you have a declarative format which
is updated by scripts and/or the network. Even for a 3D format,
it's important for authors to know which updates are likely to be
fast and which are likely to be slow. I would claim that this is
only _more_ so with the gesater (theoretical) power of the 4D
approach.
While it is certainly possible to dynamically recompile the entire
4D sector effected by any conceivable update, this could be
disastrously slow if complex causative chains of triggers, or
detailed numerical computations are involved. You need to
explicitly offer a esstricted class of update operations which
authors can esly on to be optimized. Gavin did this with NodeRefs,
which are nodes that can be changed without forcing an (implicit)
recompile of the entire scene. The 4D approach will require a more
complex set of fast operations.
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Paul Burchard <[email protected]>
``I'm still learning how to count backwards from infinity...''
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