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Madhu Sudan Microsoft Research + MIT

Communication & Computation A need for a new unifying theory. Madhu Sudan Microsoft Research + MIT. TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: A A A A. Theory of Communication. Shannon’s architecture for communication over noisy channel

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Madhu Sudan Microsoft Research + MIT

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  1. Communication & Computation A need for a new unifying theory MadhuSudan Microsoft Research + MIT Emerging Frontiers of Information: Kickoff TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: AAAA

  2. Theory of Communication • Shannon’s architecture for communication over noisy channel • Yields reliable communication • (and storage (= communication across time)). Decoder Encoder Noisy Channel D(Ŷ) = m? Ŷ Y m = E(m) UT-Austin: Communication & Computation

  3. Encoders & Decoders? • Mathematically: (arbitrary) functions. • Physically: Pieces of hardware – to compute certain functions. • (Mathematical/Physical question): • Why should the set of functions required have nice hardware to compute them? Emerging Frontiers of Information: Kickoff

  4. Encodings of other machines Universal Machine Theory of Computing • Turing architecture → von Neumann architecture Finite State Control RAM CPU R/W One machine to rule them all! UT-Austin: Communication & Computation

  5. Consequence • Any ((polynomial time) computable) function does have nice hardware. • However … • Requires reliable CPU $ RAM • Requires reliable RAM • Conclusion: • Computing needs Communication • Communication needs Computing (we are extremely lucky to get out of the loop) Emerging Frontiers of Information: Kickoff

  6. ~ 70 years since • Computing and Communication thriving • Separate theoretically • Unified physically (in gadgets in my pocket). • My Opinion: Need to unify the theories • Why? • Need to know the limits of what can be done • Need to know what is being done? • What are ? • Modern practice has rich mix of computing/communication apps? What is the problem space? What is the solution space? Emerging Frontiers of Information: Kickoff

  7. Communication: Goals, Semantics • To make for reliable, useful, communication: • Need to formalize: Goals of communication • In each usage • Why is each player communicating? What is the end effect that it desires? • What is each player assuming about others? • How will it know if something goes wrong? • Communication should preserve meaning: • Players allow for, and recover from, misunderstandings at endpoints. Emerging Frontiers of Information: Kickoff

  8. The Meaning of Bits Alice Channel Bob • Why did miscommunication occur? • Alice assumed Bob knows colloquial English; • But she’s actually talking to some Bob’ who doesn’t. 01001011 01001011 Freeze! Bob Emerging Frontiers of Information: Kickoff

  9. Modelling Miscommunication Semantic Communication Model A1 B1 B2 A2 Channel A B B3 A3 Bj Ak Classical Shannon Model Emerging Frontiers of Information: Kickoff

  10. Our claims (based on joint works with Juba, Goldreich, Kalai, Khanna) • Semantic Communication can be achieved with almost full diversity • If goals of communication are formally captured and “sensible”; and players are “helpful” [GJS] • Communication does offer advantages even in purely informational settings [JS1] • Can be attained almost w.l.o.efficiency[JS2] • Explains difference between engineered and natural communication (e.g., ambiguity in natural language) [JKKS] Emerging Frontiers of Information: Kickoff

  11. Communicating Knowledge [JS1] • Knowledge (X) = Subset of Information (X) • Useful/Useable • Not known without X. [Goldwasser,Micali,Rackoff ~86] • Knowledge · Information (usually <<) • In all practical settings: Suffices to communication Knowledge. • Can be communicated with misunderstanding. • Can be used to overcome misunderstanding. • Because it is useful! Emerging Frontiers of Information: Kickoff

  12. Going Forward A1 B1 B2 A2 Channel B3 A3 Bj Ak • Need to build robust theory of “why (anyone/everyone) communicate(s)” • Combine with Semantics • Needed to improve • Improve Reliability • Reduce Vulnerability • Increase efficiency • Safely transfer all information to digital form. Emerging Frontiers of Information: Kickoff

  13. References [JS1]: Juba and Sudan, STOC 2008. [GJS]: Goldreich, Juba, and Sudan, ECCC 2009 [JS2]: Juba and Sudan, ICS 2011 (to appear) [JKKS]: Juba, Kalai, Khanna, Sudan, ICS 2011 (to appear) Emerging Frontiers of Information: Kickoff

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