To mitigate the potential negative impact of such changes, rigorous revision management is essential, starting with the distinction between major and minor revisions and corresponding numbering schemes. Incompatible changes must then only be introduced in major revisions, after having been announced before. Inside a major revision, say, 1 .x, all minor revisions (e.g., 1. 1 , 1. 2 , etc.) are all compatible with each other. Revision 2. 0 may introduce incompatible changes, but not 2. 1. This ensures that implementers and users can easily and reliably decide whether a specific question or test can be processed or not.