ACTS uses Semantic Versioning to indicate breaking changes in its public API. A breaking change will result in a new major version. The Conventional Commits convention is used for pull requests to track the type of changes that have been merged and ensure that the version number is increased correctly.

Since ACTS is still under active development, we create major versions that break the API relatively frequently. We try to limit breaking changes to about once a month.

Public API

The API surface of ACTS is very large. Everything at the top-level in the Acts-namespace is considered public.

Note: If a private symbol, e.g. in any namespace that contains detail, like Acts::detail, or Acts::Experimental namespaces, is part of an otherwise public API, this should be considered a bug, which we would appreciate being reported as an issue.

There are a number of optional components in the Plugins/ folder, only some of which are considered part of the public API:

Private API

The following components are not part of the public API but are expected to become part of it at a later stage:

All plugins in the Plugins directory which are not listed under Public API.
The Fatras library in the Fatras directory.
The Alignment library in the Alignment directory.

The following components will never become part of the public API:

Symbols in helper namespaces e.g. in Acts::detail must be considered implementation details and are not part of the public API.
Symbols in the namespace Acts::Experimental are not part of the public API. They are evaluated and developed, and might eventually be moved into the main Acts namespace
The examples framework and executables in the Examples directory.
All units tests, integration tests, (micro)-benchmarks, and related code in the Tests directory.