1. Foundations of Constraint Processing, Fall 2005 November 16, 2005nFCi1 Foundations of Constraint Processing CSCE421/821, Fall 2005: www.cse.unl.edu/~choueiry/F05-421-821/ Berthe Y. Choueiry (Shu-we-ri) Avery Hall, Room 123B choueiry@cse.unl.edu Tel: +1(402)472-5444 New(er) Types of AC

2. Foundations of Constraint Processing, Fall 2005 November 16, 2005nFCi2 Singleton Arc Consistency Repeat until no change occurs Repeat for each variable Repeat for each value in domain Assign this value to this variable. If the CSP is AC, keep the value. Otherwise, remove it. Proposed by Debruyne & Bessière, IJCAI 97

3. Foundations of Constraint Processing, Fall 2005 November 16, 2005nFCi3 Neighborhood inverse consistency Repeat until no change occurs Repeat for each variable Consider only the neighborhood of the variable Repeat for each value for the variable If the value appears in any complete solution for the neighborhood, keep it. Otherwise, remove it. Proposed by Freuder & Elfe, AAAI 96