Cees de Groot wrote:

>Could you explain a bit about the Gemstone model you are referring to?
>I only have marginal GS exposure, and I'm sure that I'm not the only
>one.
>  
>
Its been a while, so I may be missing some of the details...

Gemstone keeps multiple versions of classes in the image, each in a 
linear collection of versions. Instances can hop rom one version to the 
next lazily (or be pushed) and custom methods are written to specify how 
variable values should change. Such a conversion would happen in a 
transaction, therefore every instance is consistent - in one version or 
the other.

So this gives a framework for making class evolution happen in a nice 
orderly manner, without data loss or even significant downtime/delays. 
This is clearly a priority if we remember GS is a database, but 
never-ending image transformations or recompilations are a bane for us 
too. Certainly when stopped half way through... ;-)

These are not our top issues to solve, and almost certainly not the 
techniques we need to use, but its worth remembering that solutions are 
out there. Alan Lovejoy's recent message sounds more directly relevant.

Daniel Vainsencher