How schedworld-II differs from schedworld.

    Schedworld-II has some control rules which enforce the following domains
axiom.  If an operation fails backtracking to re-schedule a previous
operation that was at time t to time t+n n>0 will not cause the original
failure to go away.  For example if you paint object A at time 1, but can't
clamp object B at time 2 then trying to paint object A at time 2 and clamp
object B at time 3 must also fail.  The control rules added do not permit
this failure paths to be explored.  This can decrease the size of the search
space by several orders of magnitude which allows much more complex problems
to be explored.

Also, the functions which generate objects for weld and bolt will return nil
when you try to bolt or weld an object to itself.  In the past this was not
the case, and so a few extra alternatives which would necessarily be
failures where generated.

You can get the old functions by loading the functions file from the other
domain.  You can get the old sc-rules.lisp by loading the old sc-rules.lisp
file and calling (load-domain).

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	Schedworld is a machine shop scheduling domain. There are several 
machines in the shop, corresponding to several actions in the domain.  Each
machine can operate an object at a time, only if the machine is IDLE and the
object is FREE.  We would like to perform some of the above operations in an
object. But there are some restrictions in the time at which we can use a
machine. For example, ROLLing an object makes the object hot, and since some
machines will not handle hot objects we would have to wait for some time to
schedule a machine for a hot object. PRODIGY has to find an acceptable
sequence of machines to perform the required operations in an object. 

	Each operator corresponds to a machine, i.e. an operation to be 
performed on the object. These are the following: POLISH, ROLL, LATHE, 
GRIND, PUNCH, BOLT, WELD, SPRAY-PAINT and IMMERSION-PAINT. Some of these
machines can CLAMP the object.


	The interesting features of this domain are: 

   - there is a lot of goal interactions.

   - this is the only domain in Prodigy where time is involved.

   - this domain has been extensively tested with the EBL module.
