On Fri, 2005-03-18 at 13:45, Brian Lloyd wrote:
> A lot of time was spent talking about these (legitimate) concerns - 
> unfortunately it will probably take a little time to distill all 
> of that communication to the community. But let me take a shot ;)
> There are several different groups, with different goals and 
> concerns, who are involved here:
>   A: Z2 developers that don't care right now about Z3
>   B: Z2 developers that care about Z3, but can't effectively 
>      use anything Z3 related right now because it is not practical 
>      or possible to switch wholesale and there is no bridge to 
>      Z3 that doesn't require throwing away existing investments 
>      in Z2
>   C: Z3 developers that don't care about Z2 anymore, often because 
>      they dont have existing investments in Z2
> There are a significant and growing number of people in group B. 

Yup, that makes sense.  Are these assumed to also be the folks who will
try to make sure that new Z3 releases make it in to Z2 via Five?  I
guess what I'm driving at is that I'd hate to eventually have a very old
version of Z3 sitting inside of Zope 2 due to insufficient bandwidth on
the part of those developers to keep up with Z3 releases.  While it
wouldn't be the end of the world or anything, I suspect some
dependencies will inevitably creep into the Zope 2 core on Zope 3
packages, and maintaining an older codebase can be pretty painful.  The
testing requirements for making sure that changes that Z2 coders make to
Z3 work both in Z2 and Z3 is a pretty high bar, just as vice versa.  In
the past, I've seen efforts like this turn into an effective fork as a

> At the paris sprint, we were looking for a way to:
>   - Allow folks in group B to start taking advantage of (and 
>     developing an interest in and contributing to!) Zope 3 
>     technologies
>   - Make sure that group A would not be 'forced' to do anything
>     they don't want to do
>   - Make sure that group C would not be 'forced' to do anything 
>     they don't want to do
> I feel that the approach of integrating Five into Zope officially 
> does a pretty good job of meeting those goals. We added the Five 
> product and a snapshot of Zope X3.0 into the core so that people 
> could have a reliable baseline 'out of the box'.
> That integration touched almost nothing in the Z2 code (one or 
> two things that were previously done as monkey patches were 
> un-monkeyed, but that's about it).
> The Z3 code (and the Five code) just sits there unused unless you 
> choose to use it, so Zope3 code breaking Z2 apps is not really a 
> concern.

That's good to know.

>  But is there and available, so people can begin to plot 
> their own migration paths based on their own situations.

Please correct me if I'm wrong here but I get the sense that Five is
less of a "migration path" from Z2 to Z3 than a way to integrate Z3
technologies (like views and adapters) into Z2 right now.  Obviously
allowing Z2 developers to use these things will give them a some needed
familiarity with Z3 if they decide to switch but the migration path to
"straight Z3" will always be more or less a rewrite, no?

> Like other areas of Z2 (and Z3, for that matter), contributors 
> tend to develop areas of expertise. A new area of expertise for 
> Z2 going forward will be the Five/Z3 integration, and there will 
> be a set of devs who will likely focus on that aspect. I don't 
> expect that the fact that Five and Z3 integration exists will 
> make life any harder for someone who focuses on purely Z2 
> aspects of the core anytime soon.
> So the short answer is, we tried really hard to make sure to 
> take an approach where z3 integration would not actively break 
> zope2 in any way or force people into any particular direction.

Excellent, that's what I was hoping.

> I *do* expect these (good) questions to recur in future Z2 
> releases, as integration and ability to use Z3 technologies 
> increases, but we'll have plenty of time to work those out.
> For now, I think it is a huge win to make some Z3 avenues 
> available to people who want to use them, without forcing 
> everyone to drink the kool-aid at once ;)

Yup... I'm still a bit skeptical but if other folks are committed to
maintenance I'd be less so.

- C

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