Sep 12, 2007
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- Next topic
	- Knowledge representation and reasoning

- To get into KR & R
	- lets bring in a topic that will help bridge from search to KR &R

- That topic is "satisfiability"!

- Boolean satisfiability problems
	- Given a set of clauses
		- each clause is an OR (disjunction) of boolean vars
		- there is an implicit AND between them
	- Find 
		- a satisfying assignment if one exists

- What problems can be formulated as satisfiability?
	- An example with map coloring

- How to solve satisfiability problems
	- Simple purge and explore techniques
	- basis of DPLL algorithm

- Recognizing if a problem is unsatisfiable
	- an example with reasoning

- Connections to theoretical physics
	- transition between P and NP-completeness
	- if each clause has 2 variables, it is in P
	- for 3 variables or more, it is NP-complete
		- where does the transition lie?
			- a sharp boundary