Transducers

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# Transducers - PowerPoint PPT Presentation

Transducers. Jacob Dison. What is a transducer? . Defined as a device that converts one form of energy to another. Examples: Motors, Speakers, Microphones, Antennas, Light Bulbs, Potentiometer, Gauges… Essentially Sensors and Actuators . Finite-State Transducers .

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### Transducers

Jacob Dison

What is a transducer?
• Defined as a device that converts one form of energy to another.
• Examples: Motors, Speakers, Microphones, Antennas, Light Bulbs, Potentiometer, Gauges…
• Essentially Sensors and Actuators
Finite-State Transducers
• Two tapes, one for input and one for output.
• Converts a input into an output.
• Mealy and Moore machines.
Moore Machine
• Invented by Edward F. Moore (1925 -2003)
• Wrote Gedanken-experiments on sequential machines (1956)
• Associates an output with each state of the machine.
Moore Machine Formal Definition
• (K, Σ, O, δ, D,s, A,)
• K = States
• Σ = Input
• O = Output
• s = Initial State
• A = Final State
• δ = Transition Function
• D = Output Function
Mealy Machine
• Invented by George H. Mealy in 1955
• Associates outputs with transitions.
Mealy Machine Formal Definition
• (K, Σ, O, s, A, δ)
• K = States
• Σ = Input
• O = Output
• s = Initial State
• A = Final State
• δ = Transition Function
Bidirectional Transducers
• Works in both directions
• Example: Soundex System
• Input: Kaylor
• Output: K460
• Kahler, Kaler, Kaylor, Keeler, Kellar, Kelleher, Keller, Kelliher, Kilroe, Kilroy, Koehler, Kohler, Koller, and Kyler.
Weighted Transducers
• In addition to inputs and outputs, associates a weight, which can be a number of things including time, probability, distance… etc.
Hidden Markov Models
• Nondeterministic Finite State Transducer
• Machine is hidden, only outputs can be observed.

### Questions?

References
• Elaine Rich. Automata, Computability and Complexity: Theory and Applications. Prentice Hall. 2008. 96-98.
• Emmanuel Roche, Yves Schabes. “Deterministic part-of-speech tagging with finite-state transducers.” Computational Linguistics, 21(2):227-253, June 1995.
• Cyril Allauzen, Mehryar Mohri. “p-Subsequentiable Transducers.” AT&T Labs – Research
• Mohri, Mehryar “Weighted Finite-State Transducer Algorithms An Overview” AT&T Labs – Research
References
• Pradel, Michael. “Finite-State Transducers.” Seminar on Natural Language Processing. July 6, 2007.
• Hsu, Chun-Nan., Chang, Chien-Chi. Finite-State Transducers for Semi-Structured Text Mining. Institute of Information Science
• Wagner, F. “StateWORKS: Moore or Mealy model?.” StateWORKS.com. April, 2005.