OpenFST notes

symbol table

• The internal representation of an arc label is an integer.
• The symbols are used for I/O purpose.
• You can store the symbols table with the FST file or not. If you do, use the options --keep_isymbols and --keep_osymbols.
• If the labels are non-negative numbers, then the symbol tables can be omitted.
• If the symbol table files are omitted in fstprint, the FST will be printed with numeric labels unless the symbol tables are stored with the FST.