DTV12 — definition of compound time coordinate is circular

In clause 10.6.3, the definition of 'compound time coordinate' is:

Definition: time coordinate that combines more than one time coordinate

and the definition of 'compound time coordinate combines atomic time coordinate' is:

Definition: the atomic time coordinates jointly specify the compound time coordinate

That makes them both circular. Prefer something like:

compound time coordinate

Definition: time coordinate that is a set of atomic time coordinates that jointly indicate a time point

compound time coordinate combines atomic time coordinate

Definition: the atomic time coordinate is an element of the compound time coordinate (set)

These definitions match the first Necessity under the verb concept.

The 'set' makes the second Necessity redundant.

The third Necessity is misstated: it compares a time coordinate to a time scale.

The circular definitions are resolved more or less as suggested, and the related Necessities are revised.
Because of other changes to the descriptions of compound time coordinates that affect the same definitions, and related changes to the UML diagrams, the revised text for this issue is merged with Issue 19547.
Revised Text:
See Issue 19547.