Hi all!
Quoting Avi Bryant avi@beta4.com:
On Wed, 16 Oct 2002, [ISO-8859-1] Göran Hultgren wrote:
Ok, what about all you other people out there? Are my explanations
making any
sense? Henrik - could you please acknowledge that I haven't made any
gross
factual errors? Daniel, what do you think?
I continue to stand by the Modules codebase as a good start, but I am
always
open for improvements.
It seems to me that part of the problem with these discussions of modules is that nobody has been terribly clear about what they hope to get out of them. Perhaps if we make our goals clearer, it will be easier to talk about the possible solutions. Here are a few things that I would think
Yes, good point.
a module system might provide:
- A way to specify related pieces of code. This has to
include both entirely new classes and patches/additions to existing classes. Let's call these "packages". 2. A way to easily save and load these packages to and from easily distributable files. 3. A way to cleanly update an image with a new version of a package. 4. A way to cleanly unload a package from an image. 5. A way to analyze dependencies between packages. 6. A way to specify dependencies between packages. 7. A way to protect packages from name clashes. 8. A way to organize packages hierarchically.
IMO, 1-3 are the most important. Not surprisingly, these are also what DVS mostly provides, although it works better for straight additions to existing classes than for patches to them. The interesting thing is that this can be provided without any changes to the base image, as a simple addon package.
Since 3.2 will be the stable release for quite some time this is good to hear. I still have to look into DVS.
A sidenote: One reason for the Modules work being so... uncoordinated is the lack of a good "CM" tool like CVS or similar. Would you say (I trust your word) that DVS is the best thing going in this respect for Squeak currently? If that is the case, then perhaps we should consider using it for all the Modules-related cooperative work that needs to be done in 3.3. Currently there are a whole slew of .cses floating around that needs to be integrated etc. The lack of something CVS-ish (and I am talking about the very simple update/commit-cycle) is IMHO a big hurdle for real cooperative development in the Squeak image and the Modules area is a good example where we really need this.
Even more on the side: Of course what I REALLY would want is an interactive update/resolve conflicts/commit-cycle using DeltaModules in 3.3 thus creating the CVS-optimistic-concurrency model of development with intelligent conflict resolution tools instead of simple "oops, those lines are too close"-logic. And then coupled with a bit of realtime feedback inside the browsers on who is doing what and where and you have my wet dream of a CM system...
4, I think, could also be done fairly easily on top of 3.2, but it seems much less important to me: once I've loaded something into an image I rarely want to remove it. If I'm testing a new package, I use a throwaway image. I guess that assumes a minimal base image to load things into.
:-)
Daniel has already done 5, again in 3.2. I don't see why 6 would be very difficult - it ties into what Daniel and I were talking about with subclasses of Module to store metadata. 6 also seems like something that SqueakMap might be extended to do.
True but I have steered away from that since I didn't want to duplicate efforts - Modules already has functionality for it.
It would be a pity if people started to "rebuild" stuff (that is already implemented partly in 3.3 Modules) in 3.2 instead of helping out and finishing the job in 3.3...
7 is, of course, the big one: it is the real justification, as far as I'm concerned, of the work that's beem put into 3.3a. But how big a deal is it? Are people routinely struggling with naming conflicts? I tend to throw a 2 letter prefix in front of my class names and forget about it. But maybe that's just me.
I agree but if you have read the Swiki pages about Modules you realize that there are a lot of cool stuff there. The ability to separate loading from activation, working on different versions of classes/modules, clean atomic stages of downloading all dependencies, loading them all into the image and finally activating it all, the global namespace and so on.
8 would be nice, but the major benefits (being able to load/unload groups of packages at once) can be gotten through dependecies + dummy packages, the same way most of the linux packaging systems work.
This is a highly personal take on things, of course - I'm not pretending that these preferences will be the same for everyone. I'd be curious to hear what, for example, Stef's or Henrik's version of this list would look like. But me, I'd rather see a lightweight module system in 3.2 without namespaces or hierarchy get widely used first, and then start to think about the full Module system a la 3.3a.
Perhaps the combination of SqueakMap (soon coming in 3.2 updates) and DVS would work as a good lightweight solution for 3.2. But I still think we should push ahead on 3.3 Modules.
Oh yeah, forgot to add my list. One thing off the top of my head though: Image building instead of image stripping. That is a biggie in my book.
regards, Göran
Göran Hultgren, goran.hultgren@bluefish.se GSM: +46 70 3933950, http://www.bluefish.se "Department of Redundancy department." -- ThinkGeek