What version numbering scheme to use?
I'm looking for a version numbering scheme that expresses the extent of change, especially compatiblity.
Apache APR, for example, use the well known version numbering scheme
<major>.<minor>.<patch>
example: 4.5.11
Maven suggests a similar but more detailed schema:
<major>.<minor>.<patch>-<qualifier>-<build number>
example: 4.5.11-RC1-3732
Where is the Maven versioning scheme defined? Are there conventions for qualifier and build number? Probably it is a bad idea to use maven but not to follow the Maven version scheme ...
What other version numbering schemes do you know? What scheme would you prefer and why?
Answer
Here is the current Maven version comparison algorithm, and a discussion of it. As long as versions only grow, and all fields except the build number are updated manually, you're good. Qualifiers work like this: if one is a prefix of the other, longer is older. Otherwise they are compared alphabetically. Use them for pre-releases.
Seconding the use of semantic versioning for expressing compatibility; major is for non-backwards compatible changes, minor for backward-compatible features, patch for backward-compatible bugfixes. Document it so your library users can express dependencies on your library correctly. Your snapshots are automated and don't have to increment these, except the first snapshot after a release because of the way prefixes are compared.