jbn@wdl1.UUCP (jbn ) (09/27/84)
Apollo has a nice approach in their Domain Software Enginering Environment. It is possible to have files with multiple versions; there are SCCS-like utilities for maintaining them, the versions are maintained with backward differences (the latest version is present in its entirity and old versions exist as differences from the latest one) and the operating system has mechanisms for reading the latest version of such files and preventing programs that don't know how to update them from changing them.