Split BT-s?

[ChristianeCPeters]

In the CELEX -no matter what version- theBT-s are groupt within each BG and the colums give Info in which notive Type the BG/BT is Optional, Conditionaly Mandatory, Existing Mandatory or Mandatory. So far so good.
None of the BTs or BGs are devided in the CELEX. In the SDK -also different Versions- however, ther are Rules for different "Parts" of BTs. Eg. BT-09 a and BT-09 b or BT-712 a and BT-712b. Where do theses divisions come from and where can Info on the parted BTs can be retrieved?

[bertrand-lorentz]

Please see this page for explanations on why there sometimes are several fields for one BT:
https://docs.ted.europa.eu/eforms/latest/fields/index.html

As indicated there, for each field we indicate in fields.json the identifier of the BT to which the field corresponds.

As this is rather a question, I'm converting this to a "discussion".