CDS activation not possible because of semantic key

HI,

we created a BO with 3 tables.

now as i am adding the ObjectModel annotations it gives an error for the semantic key.

Semanitc key is not a DB field - but acutally it is.

I tried the semantic key without alias - error

and with alias name

again error

basic view is defined as

How can this be resolved?

Undo the alias in the basis view is also nearly unpossible due to the usage in the transactional views