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Backward compatibility is a reasonable concept, but it is given
peculiar emphasis in the software world. Specifically, users and
developers often expect that anything they’ve ever done will continue
to work, forever, in exactly the same way. And if you’re a software
engineer, providing applications to users or a platform to developers,
the onus is on you to ensure that these demands are met. It’s rather
like asking Picasso to continue producing satisfying, powerful works in
all of his previous styles in addition to his current fancy.
“Eh, Pablo? This kids-crayon stuff is crap. We need another one of
your blue-period paintings. Oh, and one of the boxy ones would be
nice, too. By next month. Thanks.”