Backwards Compatibility
The LSB is designed to be binary-compatible and produce a stable application binary interface (ABI) for independent software vendors. To achieve backward compatibility, each subsequent version is purely additive. In other words, interfaces are only added, not removed. The LSB adopted an interface deprecation policy to give application developers enough time in case an interface is removed from the LSB. This allows the developer to rely on every interface in the LSB for a known time and also to plan for changes, without being surprised. Interfaces are only removed after having been marked "deprecated" for at least three major versions, or roughly six years.
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