Quote - >> This is because Apple went out of their way to insure as much backwards compatibility as possible under their circumstances (hence "Classic", Carbon Libraries, etc), and Adobe went out of their way to do the same with their apps. Not everyone has that luxury.

Uh, no. That's not how an Illustrator or a Photoshop file works, so your explanation is essentially useless, not to mention incorrect.

Oooookay....

Here' let me boil down what I'm getting at. Just as much as an OS won't understand an app that contains calls for now-missing APIs, a data file can easily contain calls for now-missing functions within the app trying to open it. Replace "now missing" with "repurposed", and you've covered 90%+ of all eventualities when it comes to losing backwards compatibility.

Quote - But the Illustrator system of vector points has not changed in over twenty years, which is why things built in 88 can still be viewed in CS2.

Because, quite simply, a list of vectors are pretty freakin' easy to carry forward. Now if you're trying to carry forward a bit of data that relies on an algorithm that no longer exists in the new version?

I know, I know - you're going to say "well they should just keep it!", but it ain't that easy. One reason it could disappear is because of security reasons. Another is because that algorithm is no longer supported by the current operating systems. Another still is the desire to reduce bloat.

If programmers followed your advice, you get (drum roll please...) Windows Vista - something that desires so much backwards compatibility that it often eats (on average) 600+ MB of RAM just to run itself.

Quote - backwards compatability was a business necessity, just as it is in Poser.

Sure it is - but how often do you have to open a Poser 1 file?

/P