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Re: Re: Re: Re: Apocalypse 12

by BrowserUk (Pope)
on Apr 20, 2004 at 00:28 UTC ( #346496=note: print w/ replies, xml ) Need Help??


in reply to Re: Re: Re: Apocalypse 12
in thread Apocalypse 12

I agree wholeheartedly with your reservation regarding versioning.

Any library, module or class exports two things. It's interface, and it's implementation. Whilst the implementation can go through versions, the interface cannot.

Once defined, even before implementation, an interface becomes fixed. If the interface later varies, it becomes an new interface. Anything written to comply with the old interface will need to be adapted to use the new one, no matter how small the change.

You can dress the new version's name up by applying a version number to the old name, but that simply means that the name of the new interface looks superficialy, but misleadingly similar to the old one.

Even if the new interface is a proper superset of the old interface, it still means that code using either are forced into making loadtime or runtime tests to determine which version of the interface they have access to. In the case of existing code, connecting to the new version, if it remains unmodified, there is the possibility of conflict between new features of that new interface and existing features or extensions added by the pre-existing caller.

In the case of new code that doesn't now whether it will have the new or old version of the interface at runtime, it must then add code to test for teh availability of the new features and either fail if it doesn;t have them r supply alternatives.


Examine what is said, not who speaks.
"Efficiency is intelligent laziness." -David Dunham
"Think for yourself!" - Abigail


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