Finite State Transducers FSTs

1
Finite State Transducers (FSTs)

• Recogniser
• Input stringpair
• Accept if stringpair is in stringpair language
• Otherwise reject
• Output yes/no
• Generator
• Output stringpair
• Translator
• Input one string
• Output another

2
FST Components

• S s1, , sN a finite set of N states
• K k1, , kM a finite alphabet of M complex
  symbols (alphabet)
• Complex symbol input-output pair (i o)
• Input symbol from alphabet I
• Output symbol from alphabet O
• s0 start state F set of final states
• d(S, IO) transition function
• FSA K a, b, !
• FSA K (ab), (ba), (!!)

3
FST Tapes
Input tape
Output tape
4
FSTs
DFST
NFST