Lecture 11: A Focusing Prover

We review the idea of focused search and present the ML code for a simple propositional focusing prover. It is based on fixing the don't-care non-deterministic choices simply based on the order of assumptions and solving don't-know non-determinism through bounded depth-first search and iterative deepening.

Reading

• Handout 8 on Focused Derivations, pages 65-67 (also availabe in PDF format).
• Slides from the lecture.
• Browse several implementations of a simple theorem prover for propositional intuitionistic logic using focusing derivation (or retrieve as gzipped tar file).

Key Concepts

• Focused derivations
• Backtracking
• Success continuations
• Depth-first search
• Bounded iterative deepening

Links

• Previous lecture: Focused Derivations
• Next lecture: Residuating Equality