class ViewModel::AccessControl

def valid_edit_check(_traversal_env)

implementations.
edit checks the opportunity to compare values. To be overridden by viewmodel
transactional backing models, the changes may be made in advance to give the
attempted changes are permitted in the given context. For viewmodels with
Once the changes to be made to the viewmodel are known, check that the 
def valid_edit_check(_traversal_env)
  Result::DENY
end