What's a POS??

Mike McDonald mikemac@titian.engr.sgi.com
Thu, 08 May 1997 19:20:38 -0700

  It seems in this discussion about POSes, everyone is assuming that a
PSO is whatever they've always assumed a POS was. The rest of us
haven't the foggiest idea what YOU mean by a POS. So here's some
questions about POSes that I'd like you guys to answer so we can
figure out what your POS is.

Is a POS completely transparent to the programmer and user? The old
Xerox Interlisp machines used something like this. You just did your
mornal lisp things and then the system saved everything for the next
time you came back around. This is the dumplisp/checkpoint approach.
How fine a granularity does your checkpointing have? How do you handle
different things wanting different granularities?

If not the above, then does the object builder or the object user
determine if the object is persistant? Ie, does the object have to be
a special kind of object (maybe a CLOS object with a particular base
class) or can I tell the POS system to "save" any ole object?

If it's the latter, how do you determine where the object ends and
some other object begins? If you aren't careful, you're going to
implement dumplisp. :-)

 Thanks for the info,

  Mike McDonald