Within a relationship one side has been marked as dependent, e.g. the instances referenced in the relationship depend on the relationship. Removing instances from a depending Relationship is possible from the reference within the dominant instance, only.
The accounts of a bank in general depend on the bank. This can be defined the following way:
structure Bank { relationship accounts {inverse=bank_ref; depend=YES} }
structure Account { relationship bank_ref {inverse=accounts; depend=NO} }
In this case it becomes possible to remove an account from the accounts-reference within the bank instance (with the consequence, that the account will be deleted because it depends on the relationship). It is however, impossible to remove the bank instance from the reference within the account instance, which depends on the relationship.