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From Jason van Zyl <>
Subject Re: POM interoperability
Date Tue, 02 Nov 2010 09:45:59 GMT

On Nov 2, 2010, at 8:25 AM, Brett Porter wrote:

> On 01/11/2010, at 6:37 PM, Jason van Zyl wrote:
>> At any rate if anyone has ideas or documents I'll integrate it into the proposal
I'm writing. I'm moving pretty fast and I plan to release a version of the Maven Shell next
week, and then a couple weeks later a version with Polyglot capabilities. So if you have thoughts
I'd appreciate them sooner rather then later.
> Not had time to read all the mail on list in the last few hours, but in the interest
of sooner rather than later...
> I've posted some thoughts on this to the list before, and planned to dig it up by Wednesday
for the meetup. I'd also hacked together support into the branch of 2.x that works with attributes.
At the most basic, I'm thinking we should deploy a trimmed version under the 4.0.0 model to
the repository as the interchangable format under the current layout, then the actual model
as it stands at the time separately.

You have absolutely no idea how the information would be used. Why would you, as a first step,
reduce the model before you even know how it's going to be used.

To me the order of precedence is:

1. vN model to vN model translation. Albeit no one here may be interested in that because
it's specifically for Polyglot but this one is relatively simple. Straight up translation
and deployment of both models.

2. vN+1 to VN model translation. This is what we should be most interested in for 3.1. where
the operating model for Maven 3.1 (4.1) must be downgraded to operate with Maven 3.0/2.2 (4.0.0)
and both models deployed.

Let's please be realistic about the work that's going to be done. Selective reduction of the
model is a nice idea but not required, and not going to impact interoperability. That's a
nice to have in the future but we should be pragmatic and tackle the simpler forms of interoperability
before tackling something more complicated.

> It would be nice to consider a long term migration to extensible metadata for this aspect
of the repository, while retaining original artifacts as a separate file.

Again, we should start simple. We have consider forward and backward metadata in p2 repositories
and that is a lot of work and a ton of testing. I've absolutely no evidence here in the last
year that this project can deliver that. I would propose we do work with the p2 folks as their
repository metadata format is more sophisticated then ours and ultimately merging the metadata
models would make sense as then we have a whole other body of developers working on the problem.

But seriously, I urge folks to be pragmatic and tackle the simple models of interoperability.
We don't need to boil the ocean to make 3.1 work. I think model reduction while coming up
with a plan for interoperability is a recipe for disaster.

> Cheers,
> - Brett
> --
> Brett Porter
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Jason van Zyl
Founder,  Apache Maven

What matters is not ideas, but the people who have them. Good people can fix bad ideas, but
good ideas can't save bad people. 

 -- Paul Graham

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