Known on the Windows platform as "DLL hell", an incompatible updated library will break executables that depended on the behavior of the previous version of the library if the newer version is incorrectly not backward compatible. A program, together with the libraries it uses, might be certified (e.g. as to correctness, documentation requirements, or performance) as a package, but not if components can be replaced (this also argues against automatic OS updates in critical systems; in both cases, the OS and libraries form part of a qualified environment).