So, is there a way to get a strong typed relation name? I mean like a const or enum somewhere?

As far as I know, that's not available, but you can add it yourself using templates.

The main difficulty is: how would you name a relation? It's not as trivial as you might think, because consider Customer - Address, where you have two of them: one for visitor address and one for billingaddress... So you often end up with the names we use for teh properties which produce the relations, e.g. CustomerEntity.Relations.OrderEntityUsingCustomerId