Not so fast, all you have to do is sprinkle some .net dust on the computer and 
everything will be fixed until the next time MS changes their mind, right?

Sorry, couldn't resist.  Ironically, I find that software written to MS specs 
breaks readily; things written with anything up through contempt for them seems 
to work just fine.  I stop short of seeing a vm as allowing one to run Windows 
in perpetuity, but that is another debate.

I frequently want things both ways. I want the rest of the world to stand still 
(except when I want something fixed<g>) so I can get on with my work, and I 
generally expect that my code will evolve such that the most recent version is 
the best I know how to make.

It is unlikely that I would be brave enough to run old versions of my code in 
the same image with new stuff, but if you can make that work to serve all of 
us, have at it :)

Bill 



-----Original Message-----
From: [email protected] 
[mailto:[email protected]] On Behalf Of Marcus Denker
Sent: Tuesday, January 26, 2010 4:49 PM
To: [email protected]
Subject: Re: [Pharo-project] Gardening/ScriptManager


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.


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