Your input is valued: ongoing discussion of new BIDS data types

[bids maintenance]

Dear BIDS-community,

We would like to gather your input on a topic which recently came up in multiple BEPs. This issue concerns the current handling of data types vs. modalities for extensions to BIDS. Yahya Shirazi wrote a very informative summary on this topic in a GitHub issue (thank you, Yahya!), pointing to BEP042 as an example. Since these questions and discussions came up in other BEPs, too, we invite you to join this discussion and provide your thoughts in the aforementioned GitHub issue. In short (copied from Yahya’s issue):

• The BIDS specification currently distinguishes between data types (represented as subdirectories under each subject) and modalities (represented as file suffixes) 

• There appears to be inconsistency in how these distinctions are made across different kinds of data

• When determining whether a data category deserves its own data type/suffix or should be incorporated under an existing umbrella, factors such as signal source and nature, technical requirements, community needs, consistency with existing structures etc. have been raised

Questions for the BIDS community:

• What should be the threshold criteria for creating a new data type vs. using an existing one?

• Should brain-derived signals be treated differently from other physiological signals? If yes, how does this differentiation apply to the current specifications, including Motion-BIDS and ongoing PRs?

• How should we balance the need for specificity against the risk of fragmentation?

• Should we establish a formal policy for what constitutes grounds for a new data type/suffix?

• How can we ensure that similar types of data (e.g., various physiological recordings) are treated consistently across the specification?

• What is the threshold or recommendation for using the data specific modality/recording versus embedding data under other modalities? For example, Eye-tracking and EMG can be embedded under EEG as channels.

Please share your thoughts in this GitHub issue before June 20th and include your own experiences with this, i.e., 

• if this discussion came up in your BEP, too

• how this discussion was handled (who was involved and how was the final decision made)

• support by maintainer involved

By this, we hope to find a more systematic approach in the future and avoid having the same but separate discussions across BEPs. 

Thank you!

Your BIDS-maintainers