EBNF describes a syntax and grammar for a domain specific language. It makes it readable for others. Mixing both expression parts, otft names and tuples into a EBNF grammar, the users of the EBNF could basically use the semantics as a language specifier.
Deriving the EBNF from classes, attributes and relations only describes the static parts of the model. E.g. The actual CRUD operations are still missing these require another level of syntax which is not part of the model.
