Semantic Versioning

The Axom team uses the semantic versioning scheme for assigning release numbers. Semantic versioning is a methodology for assigning version numbers to software releases in a way that conveys specific meaning about the code and modifications from version to version. See Semantic Versioning for a more detailed description.

Version Numbers and Meaning

Semantic versioning is based on a three part version number

  • MM is the major version number. It is incremented when an incompatible API change is made. That is, the API changes in a way that may break code using an earlier release of the software with a smaller major version number. Following Gitflow (above), the major version number may be changed when the develop branch is merged into the main branch.

  • mm is the minor version number. It changes when functionality is added that is backward-compatible. The API may grow to support new functionality. However, the software will function the same as any earlier release of the software with a smaller minor version number when used through the intersection of two APIs. Following Gitflow (above), the minor version number is always changed when the develop branch is merged into the main branch, except possibly when the major version is changed.

  • pp is the patch version number. It changes when a bug fix is made that is backward compatible. That is, such a bug fix is an internal implementation change that fixes incorrect behavior. Following Gitflow (above), the patch version number is always changed when a hotfix branch is merged into main, or when develop is merged into main and the changes only contain bug fixes.

What Does a Change in Version Number Mean?

A key consideration in meaning for these three version numbers is that the software has a public API. Changes to the API or code functionality are communicated by the way the version number is incremented. Some important conventions followed when using semantic versioning are:

  • Once a version of the software is released, the contents of the release must not change. If the software is modified, it must be released as a new version.

  • A major version number of zero (i.e., is considered initial development where anything may change. The API is not considered stable.

  • Version 1.0.0 defines the first stable public API. Version number increments beyond this point depend on how the public API changes.

  • When the software is changed so that any API functionality becomes deprecated, the minor version number must be incremented.

  • A pre-release version may be denoted by appending a hyphen and a series of dot-separated identifiers after the patch version. For example, 1.0.1-alpha, 1.0.1-alpha.1, 1.0.2-0.2.5.

  • Versions are compared using precedence that is calculated by separating major, minor, patch, and pre-release identifiers in that order. Major, minor, and patch numbers are compared numerically from left to right. For example, 1.0.0 < 2.0.0 < 2.1.0 < 2.1.1. When major, minor, and patch numbers are equal, a pre-release version has lower precedence. For example, 1.0.0-alpha < 1.0.0.

By following these conventions, it is fairly easy to communicate intent of version changes to users and it should be straightforward for users to manage dependencies on Axom.