PMP will use semantic versioning. This is documented in detail at semver.org, but a summary follows.
Version numbers will follow the pattern major.minor.patch.
Major versions start with 0.x.x, where 1.0.0 is the first production quality release. While the major version is zero, anything may change at any time. As soon as the public API is stable, consider moving to 1.0.0. When the major version is incremented, the minor and patch versions reset to zero.
Minor versions are for feature improvements that are backward compatible with the zero release of that major version, so that 2.3.0 must work with software intended for 2.0.0, but software intended to work with 2.3.0 may not work with 2.0.0. When the minor version is incremented, the patch version resets to zero.
Patch versions are for emergency fixes to minor versions, and must be backward compatible with the zero release of the minor version.