🚀 go-pugleaf

In article <5357@holden.lulea.trab.se> jbn@lulea.trab.se (Johan Bengtsson) writes:
>Put differently: the database ID total order and the corresponding
>transient pointer orders must be order-isomorphic (look it up, I did :-),
>to ensure that the total pointer order for the addresses of
>persistent objects mapped into transient memory is consistent between
>different runs of the same program.

Aren't we talking about a total ordering that is consistent for the
duration of the process?  The OODBMS objects can have an ordering that
is persistent, but obviously the transient objects won't have a persistent
ordering.  Do we care if the ordering of persistent objects is the same
between different runs of the program?  Am I missing something?

And as I said in an earlier post (which you might not have read when you
posted this), several OODBMSs allow multiple handles on the same object.
Furthermore, Objectivity (for example) has a handle in which the actual
address of the object in core is swizzled.  This swizzling is safe
because it is private to the handle, and the user's program never sees
the address of the actual object (if he is practicing safe programming).
In fact, the object might not be in core even if the handle is valid, and
the address in core may change unbeknownst to the user.  So the user
does not have the address of the object, so he won't be comparing
C++ pointers to these objects.  And in fact, comparing the address of
the actual object will not give you the consistent ordering for the
duration of the process unless you explicitly restrict the capabilities of
the OODBMS.  Since this is all OODBMS specific, it is much better to
let the OODBMS manage the ordering and forget about trying to get an
ordering out of whatever handles it gives you.

All that long-winded explanation aside, I would like to be able to 
define a total ordering on my objects - my persistent objects (stored in
various OODBMSs) and my transient C++ objects - that is consistent for
the lifetime of the objects and the duration of the process.  I don't 
have any specific need for it at the moment, but I expect I would use this
if I had it available.

Stuart

--
: Stuart MacMartin                                    email: sjm@bnr.ca      :
: Bell-Northern Research                              phone: (613) 763-5625  :
: PO Box 3511, Stn C, Ottawa, K1Y-4H7, CANADA    Standard disclaimers apply. :