controlled vocabulary Theme

[idevisser]

it seems that the use of code list http://publications.europa.eu/resource/authority/data-theme is enforced here by a reference to must .
In addition, the use of the INSPIRE theme code list is allowed, which does not seem to be in line with the reference to must .
This is unclear. A reference to AT-LEAST seems more appropriate here and also desirable.

[jakubklimek]

This is still an open issue in DCAT-AP