Hi Philippe,
Thanks for reaching out!
Regarding your question, we recommend using the “Specify 5” tables, collectionobjectattribute and collectingeventattribute, by default. These tables are the ones we currently support and encourage users to use despite the Specify 6 tables, collectionobjectattr and collectingeventattr, being included in the database.
These *attr tables were part of an earlier plan (>15 years ago) that was never fully developed. We discourage using these tables and instead point users to the *attribute tables for their needs.
Regarding your corollary question, we may eventually mark the *attr tables as deprecated and remove them from the schema in a future release. However, they remain in the current version, and we have no plans to remove them at this time. The *attribute tables, however, are here to stay.
If you require a one-to-many relationship, we recommend using the *property tables, such as collectionobjectproperty and preparationproperty, which are designed for such cases.
The guidance to use the collectionobjectattribute relationship and table still stands!