}

sub usage {
    return 
	"\n" .
	"Usage: dia2abg.pl --diagram_name <diagram_name> [options]\n" .
	"Options:\n" .
	"\t--dia_input_file  <dia_input_file>\n" .
	"\t--dia_output_file <dia_output_file>\n" .
	"\t--component_list_file\n" .
	"\t--create_component_list\n" .
	"\t--create_ibg\n" .
	"\t--debug\n" .
	"\t--ibg_file <ibg_file>\n" .
	"\t--change_flow_causality <bond causality spec>\n" .
	"\t--change_effort_causality <bond causality spec>\n" .