Sophia has two versions: release version and storage format version.
Release version is the current version number. Sophia uses a common practice for version naming: major.minor.latest_fix_number.
Current release version can be read from sophia.version variable.
Storage format version follows the same rule. The number of version is equal to the previous Sophia version, that contains modified storage format.
Current storage format version can be read from sophia.version_storage variable.
Any Sophia releases are storage format compatible if storage versions are equal.