BIDS is a structure for organizing data and metadata. There are some BEPs that go beyond this to do something quite different:

• BIDS StatsModels (BEP 002) is a specification of intended processing. While how to name stats models fits neatly into the existing format, the file contents are somewhat tangential. Consistency with BIDS variable (TSV column) naming schemes and conventions is a general goal, and so it makes sense for this to depend on BIDS, but to include this in the BIDS spec would preclude backwards-incompatible changes. A separate versioning scheme for the models would make it easier to put out usable results.

• The above discussion can probably be applied nearly word-for-word to computational models. I'm not quite sure of the status of that effort.

• The transform file format (BEP 014) is somewhat similar. It internally has little need to reference BIDS names, so is almost wholly independent except that it would be nice if BIDS permitted it as a valid extension. And again, format versions do not need to be on anything like the same timetable as BIDS proper.

In addition to the above, where to put these in the actual structure of the specification is unclear. Transformations may be considered modalities, but model specifications are harder to wedge in. To add these coherently, I believe the current spec would need to become a subsection of a larger structure. It probably makes more sense to think of these as related but not fully subordinate.

Assuming this seems reasonable there are some questions:

1. Where should these specifications live?
2. How should we link to them on the website and main spec?
3. How should maintenance of these specifications be handled, if differently from the main specification?