Constraint Satisfaction Problems/Programming ZUI 2012/2013

Consistency checking in CSP until now – passive checking whether the constraints are satisfied Where? When? Remember the scheme of the algorithm?

Consistency checking in CSP until now – passive checking whether the constraints are satisfied Where? When? Remember the scheme of the algorithm?

Binary CSP unified structure of CSP instances all constraints are binary can we formalize all CSP problems with binary variables? constraints can be represented as a graph nodes – variables edges – constraints between variables

Consistency nodes edges / arcs

Consistency nodes unary constraints are reflected in the domain of the variable every value in the domain satisfies all unary constraints edges / arcs directed v i → v j for every x from v i domain there exists a value y from v j domain that satisfies all constraints between v i and v j

Arc Consistency make each edge in the graph of constraints consistent do we have some guarantees? What algorithm can we use? AC-1 AC-2 AC-3 …

Example scheduling requests to hotel rooms  list of requests (# of people, from, to)  set of rooms (# of beds) heuristics? MRV, LCV, …

Example (2) crosswords, sudoku, … representation? heuristics?

Homework assignment 2