This document captures guidelines to follow when considering a new release of the BIDS specification.
BIDS has generally followed a semantic versioning (semver) approach. The canonical semver text can be found at https://semver.org/, and an adaptation to documents can be found at https://semverdoc.org/. A specification falls somewhere between these two, as documentation does not require backwards compatibility, while software has notions of bugs and features which do not map to the reasons for updating a specification.
In both cases, edition numbers are specified as MAJOR.MINOR.PATCH, and the difference is in the rules for incrementing each edition number.
In BIDS, we have considered a major release version (the next being 2.0.0) to indicate backwards-incompatible changes, while minor and patch releases must be backwards compatible.
Once a decision for a release has been established, the rules of decision-making govern the mechanism of doing the release, i.e., waiting 5 business days and obtaining the approval of at least one maintainer before merging.
A minor release should be made when a BEP (BIDS Extension Proposal) has been merged into the specification. The BIDS Maintainers have discretion to identify other cases justifying a minor release.
Patch releases will generally be more frequent, and indicate less significant changes to the specification. The following is a non-exhaustive set of justifications for a patch release:
- A modality field has changed and the bids-validator has been updated to reflect this change.
- Links or information in the specification are no longer accurate, e.g. if a BEP document is added or moved
- The rendering of the specification has changed
- A metadata field or file type is added at the request of a curator attempting to release BIDS-compliant data
Ultimately, all releases are a matter of maintainer discretion, but patch release frequency should balance community needs for stability and responsiveness.