6.3.2 Syntax and Semantics

An MLF consists of one or more individual definitions. Blank lines in an MLF are ignored but otherwise the line structure is significant. The first line must contain just #!MLF!# to identify it as an MLF file. This is not necessary for use with the -I option but some HTK tools need to be able to distinguish an MLF from a normal label file. The following syntax  of MLF files is described using an extended BNF notation in which alternatives are separated by a vertical bar |, parentheses ( ) denote factoring, brackets [ ] denote options, and braces { } denote zero or more repetitions.

 
		    MLF  =  		 ``#!MLF!#''

				  MLFDef { MLFDef }

Each definition is either a transcription for immediate loading or a subdirectory to search.

 
		    MLFDef  = 		 ImmediateTranscription | SubDirDef

An immediate transcription consists of a pattern on a line by itself immediately followed by a transcription which as far as the MLF is concerned is arbitrary text. It is read using whatever label file ``driver'' routines are installed in HLABEL. It is terminated by a period written on a line of its own.

 
		   ImmediateTranscription =

				                    Pattern

				                    Transcription

				``.''

A subdirectory definition simply gives the name of a subdirectory to search. If the required label file is found in that subdirectory then the label file is loaded, otherwise the next matching subdirectory definition is checked.

 
		   SubDirDef = 		 Pattern SearchMode String

		   SearchMode = 		 ``->'' | ``=>''

The two types of search mode are described below. A pattern is just a string

 
		    Pattern = 		 String

except that the characters `?' and `*' embedded in the string act as wildcards  such that `?' matches any single character and `*' matches 0 or more characters. A string is any sequence of characters enclosed in double quotes.