This volume containsthe full papers presentedat the 12th InternationalConf- ence on Logic for Programming, Arti?cial Intelligence, and Reasoning (LPAR), held 2-6 December 2006,in MontegoBay,Jamaica.The callfor papersattracted 108 full paper submissions, each of which were reviewed by at least three - viewers. The Program Committee accepted the 46 papers that appear in these proceedings. The conference program also included 4 invited talks, by Tom Ball of Microsoft Research, Doug Lenat of Cycorp, Roberto Nieuwenhuis of the U- versidad Polit ecnica de Cataluna , and Allen Van Gelder of the University of California at Santa Cruz. Papers or abstracts for the invited talks are in these proceedings. In addition to the main program, the conference o?ered a short paper track, which attracted 13 submissions, of which 12 were accepted, and the Workshop on Emperically Successful Higher Order Logic (ESHOL). Thanks go to: the authors (of both accepted and rejected papers); the P- gramCommitteeandtheirreviewers;theinvitedspeakers;ChristophBenzmuller , John Harrison, and Carsten Schur mann for organizing ESHOL; Celia Alleyne- Ebanks for administering the conference in Jamaica; the Honorable Minister Phillip Paulwell of the Ministry of Commerce, Science and Technology for op- ing the conference (and Daphne Simmonds for introducing us to the minister); the Mona Institute of Applied Sciences at the University of the West Indies for their support; Microsoft Research for sponsorship of student regsitrations; the Kurt Godel Society for taking registrations; and EasyChair for hosting the review process.

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Independently Checkable Proofs from Decision Procedures: Issues and Progress.- Zap: Automated Theorem Proving for Software Analysis.- Decision Procedures for SAT, SAT Modulo Theories and Beyond. The BarcelogicTools.- Scaling Up: Computers vs. Common Sense.- A New Constraint Solver for 3D Lattices and Its Application to the Protein Folding Problem.- Disjunctive Constraint Lambda Calculi.- Computational Issues in Exploiting Dependent And-Parallelism in Logic Programming: Leftness Detection in Dynamic Search Trees.- The nomore?+?+ Approach to Answer Set Solving.- Optimizing the Runtime Processing of Types in Polymorphic Logic Programming Languages.- The Four Sons of Penrose.- An Algorithmic Account of Ehrenfeucht Games on Labeled Successor Structures.- Second-Order Principles in Specification Languages for Object-Oriented Programs.- Strong Normalization of the Dual Classical Sequent Calculus.- Termination of Fair Computations in Term Rewriting.- On Confluence of Infinitary Combinatory Reduction Systems.- Matching with Regular Constraints.- Recursive Path Orderings Can Also Be Incremental.- Automating Coherent Logic.- The Theorema Environment for Interactive Proof Development.- A First Order Extension of Stålmarck's Method.- Regular Derivations in Basic Superposition-Based Calculi.- On the Finite Satisfiability Problem for the Guarded Fragment with Transitivity.- Deciding Separation Logic Formulae by SAT and Incremental Negative Cycle Elimination.- Monotone AC-Tree Automata.- On the Specification of Sequent Systems.- Verifying and Reflecting Quantifier Elimination for Presburger Arithmetic.- Integration of a Software Model Checker into Isabelle.- Experimental Evaluation of Classical Automata Constructions.- Automatic Validation of Transformation Rules for JavaVerification Against a Rewriting Semantics.- Reasoning About Incompletely Defined Programs.- Model Checking Abstract State Machines with Answer Set Programming.- Characterizing Provability in BI's Pointer Logic Through Resource Graphs.- A Unified Memory Model for Pointers.- Treewidth in Verification: Local vs. Global.- Pushdown Module Checking.- Functional Correctness Proofs of Encryption Algorithms.- Towards Automated Proof Support for Probabilistic Distributed Systems.- Algebraic Intruder Deductions.- Satisfiability Checking for PC(ID).- Pool Resolution and Its Relation to Regular Resolution and DPLL with Clause Learning.- Another Complete Local Search Method for SAT.- Inference from Controversial Arguments.- Programming Cognitive Agents in Defeasible Logic.- The Relationship Between Reasoning About Privacy and Default Logics.- Comparative Similarity, Tree Automata, and Diophantine Equations.- Analytic Tableaux for KLM Preferential and Cumulative Logics.- Bounding Resource Consumption with Gödel-Dummett Logics.- On Interpolation in Existence Logics.- Incremental Integrity Checking: Limitations and Possibilities.- Concepts of Automata Construction from LTL.