Bug for Bug Compatability in IT systems.

A new system that behaves exactly like the existing system in order to allay fears and, retain all the existing interfaces, data meanings, and testing approaches. The new system's business behavior is identical and all interfaces are the same or easily adaptable. That compatibility extends to all the idiosyncracies of the previous system including all the workarounds that were put in to support other systems or rules that may or may not still be valid. This is a design of least surprise.

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Created 2023 02

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