This is part one of two posts I plan on making...although who knows when I'll get around to the massive second part :P
I've noticed something in the software world that annoys me... No one can seem to come to a clear definition of what release types mean. What exactly is an "alpha", "beta", "release candidate", etc...?
To me these namings have always had a clear cut meaning, why don't they to everyone else? I'm not going to be ridiculous enough to propose that mine are the be all end all and everyone should conform to these standards, but it certainly needs to be discussed and standardized at some point.
First off we have the elusive "alpha" release. I've always thought of the alpha stage in development to mean a work-in-progress...ie, new features are still being developed and added. The code base is at a state where you can start testing it to some extent and it's somewhat usable, but there are still new features being added, and the currently implemented ones may very well be completely rewritten depending on how tests and such go. So let's just say alpha means: The software in question is usable, but still under active development, not all features have been implemented yet, and the code is still subject to radical change. If a user is feeling really adventurous they can go ahead and give it a shot, but stability is most certainly not guaranteed.
With that definition, let's take a step back to the rarely used "pre-alpha." To me this would mean the same as alpha except it's not even usable yet, and there's no point in trying to test the software as whole yet, although specific classes and functions may be complete. Also with this definition there's no reason to really ever offer up a public release dubbed a pre-alpha. The only way an end user should ever get their hands on pre-alpha code is if they're compiling from CVS/Subversion/etc.
Next onto another commonly used term that rarely has the same meaning from project to project; "beta" releases. What defines a beta release seems to have almost no contention between different developers. To me, a beta release means that all features have been implemented and from this point on all subsequent releases will be to fix bugs and tighten up the code. It always drives me crazy when developers release their programs with a so called beta release, yet all the features are not there yet, this just isn't a beta...it's still alpha! Not only should all planned features be implemented upon the first beta release, but there should have been a reasonable amount of testing to make sure there are no major, commonly found bugs in it. A beta doesn't have to be completely stable, but it should certainly be more stable than an alpha. Now of course, this is hard to define as the beta phase is there strictly to find new bugs, but like I said, it should at least be as stable, if not more than the alpha release(s) were. Perhaps another way to look at it is that alphas are almost exclusively for developers to test, but betas are for the end users to start testing. The beta cycle of development should probably be the longest of them all as well. Sometime it takes time to find all the major bugs in your code, and there's no sense in releasing a release candidate until you've had an adequate amount of time and testers to find any show stoppers. So, to sum up my definition of beta: all features have been implemented, some testing has been done, there are no known critical bugs in the code at the time of release.
Next we have the "release candidate" or sometimes simply referred to as the "rc" for those who just can't handle typing that much. Not all projects even release a release candidate, but I think it's a good idea. Your release candidate comes after you've been in beta for a decent amount of time and all the known bugs have been found. The main purpose for the release candidate is to grab a larger group of testers than you had for your beta. As some users are too paranoid to run beta software, and many times for good reason, a release candidate is more acceptable to those who need absolute stability. Your release candidate phase doesn't have to last very long, but it should probably be more than a week (I'm looking at you Ubuntu!). Once again you should have zero bug reports open upon release of your first release candidate, as this release should..in theory...be just as stable as your final release. Of course, hopefully a few will be found before you let loose that final release, since that's the whole point of this phase. And if you're saying to yourself "what if my code doesn't have any bugs in it?" you're just kidding yourself, everyones' code has bugs. If no new bugs have been reported since your first release candidate you probably still don't have enough users testing your code.
Once the RC has been out there for a while, and you have absolutely no bugs left, then you release your final version. Now of course all development teams will have this version, but not all of them call it the same thing. Some will call it "gamma" as it's the next letter after "beta" in the greek alphabet, and many of the game developers will call it the "gold" release because of the color of the old CD-R masters they used to send off to their replicators. Of course today most of them will use the same silver-ish CD-Rs everyone else does, but the name remains. And for many developers, especially in the open source community, their code never touches a physical disc. So no matter whether you call it gold, or just "final," it's the last release you should ever make for this version number. The only complaint/suggestion I'd have here is don't rush to get to final, there's no shame in having a lengthy beta phase if that means your final is rock solid when it finally hits. Just as with the rest of this, we really should agree on one name that we all use, I prefer the simple "final" myself.
So to recap my definitions:
Pre-Alpha: code almost unusable, in heavy development, definitely not for end users
Alpha: code still in heavy development, but somewhat usable; not all features have been implemented yet, don't expect stability end users
Beta: all features have been implemented, code is fairly stable, okay for users to test at their own risk
Release Candidate: all known bugs have been irradicated, safe for all to test
Final: super stable, well tested, safe for mission critical use
In my next post I'll discuss an even sloppier area: version numbering.