The split_string_into_string_list_by_regular_expression parses the string 'a' and outputs the list ['a']. The select service displays a dialog with 'Some title' and 'Some message'. The user is only able to select the value 'a'. When the user presses OK 'a' is passed to the answer port of the select service and so to the output of the workflow. If the user clicks Cancel then a service failure is generated.