tag:
type: txt
help: Logging to a file
syntax:expression: pattern $VAR(@) "^[-a-zA-Z0-9_.]+$" ; "invalid file name $VAR(@)"
commit:expression: $VAR(./@/facility/@@) != ""; \
   "At least one facility must be configured to log messages to file $VAR(./@)"
val_help: Full path name of log file with leading slash