15-453 Formal Languages, Automata, and Computation
Lecture 22: Mapping Reductions

We finish the discussion of computation histories by showing that the question if a grammar generates every word is undecidable. We then abstract from many of the examples we have seen to develop the notion of mapping reduction which can be used to show decidability, undecidability, and related properties.

• Reading: Ch. 5.3, pp. 189-194
• Previous lecture: Computation Histories
• Next lecture: Post Correspondence Problem

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Frank Pfenning