[DGD] Why export data structures?

[Felix A. Croes]

[oops -- original response not sent to the list]

=?ISO-8859-1?Q?Petter_Nystr=F6m?= <md1pette at mdstud.chalmers.se> wrote:

> This is really just a question out of curiousity. I was thinking of coding
> something that relied on several objects having access to the same data
> structure - in this case a mapping. But then I learned that such data
> structures are made into individual copies in all objects referencing it
> at the end of the execution thread. So as I understand it, the objects
> would no longer be referencing the same data in later threads.
>
> Now, I have no reason to be upset why it works like this. I am merely
> being curious as to the reasons. Why does DGD do this? If someone's got
> the time to satiate my curiousity, I'd be happy!

That way, all data remains local to a (persistent) object.  The only
crossreferences between objects are those that pass through an object
reference, which is handled in a special way.  As a result, memory
management and swapfile allocation become much simpler and scale
better.

This is even more important for DGD/MP.

Regards,
Dworkin