On Jan 26, 2010, at 10:30 PM, Schwab,Wilhelm K wrote: > Stef, > > Are you describing something that allows different versions to coexist in one > image? Unless that's the idea (and I'm not sure I'd want to do that??)
Yes! At least I want that... we once described it like this: Backward compatibility is the enemy of forward evolvability. Nevertheless, we cannot live in a world where the old is ignored. An often overlooked property of software is that new systems can simulate the old, and the recent trends in hardware virtualization have shown that simulation of the old is far easier than for the new to stay compatible. A snapshot of an old Windows machine can run on a virtual machine forever, whereas keeping an operating system compatible forever is bound to fail. Programming languages for evolving systems should provide backwards compatibility in the same way: we need a first class description of the history of all code of the system, freeing the present from being compatible with the past while at the same time providing the possibility to go back in time easily. The system should provide complete, runnable snapshots of itself at any point in the past. Our work on changeboxes forms one first step towards this goal.... Oscar Nierstrasz, Marcus Denker, Tudor Gîrba, Adrian Lienhard and David Röthlisberger: “Change-Enabled Software Systems,” Challenges for Software-Intensive Systems and New Computing Paradigms, Martin Wirsing, Jean-Pierre Banâtre and Matthias Hölzl (Eds.), pp. 64-79, Springer-Verlag, 2008. http://scg.unibe.ch/archive/papers/Nier08bChangeEnabledSoftware.pdf The ChangeBoxes work is here: http://scg.unibe.ch/scgbib?query=Denk07c&display=abstract Marcus -- Marcus Denker -- http://www.marcusdenker.de INRIA Lille -- Nord Europe. Team RMoD. _______________________________________________ Pharo-project mailing list [email protected] http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/pharo-project
