Comments on: More on the importance of backward compatibility

By: Tortanick

Tortanick — Sun, 28 Jan 2007 18:58:35 +0000

Wouldn’t it better to use virtualiseation or compatability layers like Wine than to actually have native backwards compatability?

By: George

George — Wed, 24 Jan 2007 19:03:21 +0000

I understand and agree that backward compatibility is a highly desirable and important feature of an OS however I think that having an optimised and stable kernel is by far a superior priority ! More often that not, optimising the existing software will break bacwards compatibilty and similarly, ensuring backward compatibility often places hard limits on the optimisations possible.

If I had to choose, I would definitly have an optimised kernel even if that means loosing all backward compatibility.

Let us not loose the “evolution” concept that makes Linux so much better that competitors

By: Jim Butler

Jim Butler — Mon, 22 Jan 2007 21:55:00 +0000

I generally agree with Stephen O’Grady–throttling innovation is a potential cost of maintaining backward compatibility.

In a network protocol standards committee that I have served on, we have debated the backwards compatibility issue more than once. Most of the committee members recognized that it is sometimes necessary to break backwards compatibility in a limited way in order to make significant improvements to the protocol that improve the user experience.

By: Luis Villa

Luis Villa — Mon, 22 Jan 2007 18:06:47 +0000

Solaris most definitely does not provide a counterexample. Leaving aside how little Solaris hardware and software is actually supported to the extent MS supports Windows, the only reason Solaris has been able to move into the 90s at all is by expending massive amounts of engineering effort, and throwing out many of their own internal rules re: backwards compatibility. GNOME/JDS doesn’t have the same compatibility guarantees as CDE did, and for good reason- you can’t (or at least open source can’t yet) build modern software with the complexity and power expected by modern users without gigantic amounts of engineering effort that even Sun can only barely afford.

By: stephen o'grady

stephen o'grady — Mon, 22 Jan 2007 18:03:02 +0000

i agree with Joe Buck that there’s a definite cost to preserving ABI compatibility, but not that it’s necessarily overly complex and/or brittle software.

i see instead the primary cost as throttling innovation. ISVs and OSs alike can be held back by strict adherence to backwards compatibility – either through an inability to provide new features or a lengthened development cycle to provide them.

whether that cost is justified or not depends on your particular aims. will write more on this shortly.

By: Steve McIntyre

Steve McIntyre — Mon, 22 Jan 2007 18:00:05 +0000

Solaris also has severe problems with backwards compatibility, for example the *horrendously* old, buggy, non-POSIX version of the Bourne shell that it still ships with as /bin/sh. I’ve personally seen several people have problems shipping simple shell scripts in their packages because they have to work around this. There’s a point where backwards compatibility needs to be dropped in order to allow compatibility with newer standards that everybody else has already moved to.

Also, “run on Solaris 10 unchanged, taking full advantage of new and advanced Solaris features” is a little contradictory. To use many of the newer features, you’d have to at least rebuild…

By: Ian Murdock

Ian Murdock — Mon, 22 Jan 2007 17:20:01 +0000

Wouldn’t Solaris be the counterexample to that broadly held view, namely that binary compatibility leads to over-complex and brittle platforms? -ian

By: Joe Buck

Joe Buck — Mon, 22 Jan 2007 16:34:43 +0000

Ian: the main reason that Windows is not a rock-solid platform, far better than anything the free software world could provide, is *exactly* because Microsoft goes to such extremes to make backward compatibility work. Trying to keep every API going back to Windows 3.1 or even before working, even with bug-compatibility, results in an over-complex and brittle platform, and this detracts from the user experience.

Microsoft has hired a lot of brilliant researchers, and work coming out of their SLAM project allows one to prove that device drivers are free of a whole variety of bugs that afflict us. If they could get rid of all of their old cruft, we would have a very difficult time competing with them; their code would be virtually crash-free and ours wouldn’t be. Fortunately for us, they have a huge handicap: their installed base, their need to be backward-compatible, all the shoddy drivers shipped by third parties. Many of those old interfaces are broken by design.

So yes, we do need to care about backward compatibility, but it has to be recognized that there is a cost, and that the cost might be so great that some other consideration dominates.

By: Ian Murdock

Ian Murdock — Mon, 22 Jan 2007 16:14:33 +0000

Fair point. Perhaps I should have said “at Microsoft, the user experience comes before developer sensibilities”. -ian

By: Forest

Forest — Mon, 22 Jan 2007 16:11:42 +0000

“At Microsoft, the user experience comes first, not developer sensibilities.”

At Microsoft, the money comes first. Sometimes it takes a while for that monetary incentive to translate into improving the user experience.