Constitutes the refereed proceedings of the 13th International Conference on Logic for Programming, Artificial Intelligence, and Reasoning, LPAR 2006, held in Phnom Penh, Cambodia in November 2006. This title presents 38 revised full papers together with one invited talk.

Higher-Order Termination: From Kruskal to Computability.- Deciding Satisfiability of Positive Second Order Joinability Formulae.- SAT Solving for Argument Filterings.- Inductive Decidability Using Implicit Induction.- Matching Modulo Superdevelopments Application to Second-Order Matching.- Derivational Complexity of Knuth-Bendix Orders Revisited.- A Characterization of Alternating Log Time by First Order Functional Programs.- Combining Typing and Size Constraints for Checking the Termination of Higher-Order Conditional Rewrite Systems.- On a Local-Step Cut-Elimination Procedure for the Intuitionistic Sequent Calculus.- Modular Cut-Elimination: Finding Proofs or Counterexamples.- An Executable Formalization of the HOL/Nuprl Connection in the Metalogical Framework Twelf.- A Semantic Completeness Proof for TaMeD.- Saturation Up to Redundancy for Tableau and Sequent Calculi.- Branching-Time Temporal Logic Extended with Qualitative Presburger Constraints.- Combining Supervaluation and Degree Based Reasoning Under Vagueness.- A Comparison of Reasoning Techniques for Querying Large Description Logic ABoxes.- A Local System for Intuitionistic Logic.- CIC : Type-Based Termination of Recursive Definitions in the Calculus of Inductive Constructions.- Reducing Nondeterminism in the Calculus of Structures.- A Relaxed Approach to Integrity and Inconsistency in Databases.- On Locally Checkable Properties.- Deciding Key Cycles for Security Protocols.- Automating Verification of Loops by Parallelization.- On Computing Fixpoints in Well-Structured Regular Model Checking, with Applications to Lossy Channel Systems.- Verification Condition Generation Via Theorem Proving.- An Incremental Approach to Abstraction-Carrying Code.- Context-Sensitive Multivariant Assertion Checking in ModularPrograms.- Representation of Partial Knowledge and Query Answering in Locally Complete Databases.- Sequential, Parallel, and Quantified Updates of First-Order Structures.- Representing Defaults and Negative Information Without Negation-as-Failure.- Constructing Camin-Sokal Phylogenies Via Answer Set Programming.- Automata for Positive Core XPath Queries on Compressed Documents.- Boolean Rings for Intersection-Based Satisfiability.- Theory Instantiation.- Splitting on Demand in SAT Modulo Theories.- Delayed Theory Combination vs. Nelson-Oppen for Satisfiability Modulo Theories: A Comparative Analysis.- Automatic Combinability of Rewriting-Based Satisfiability Procedures.- To Ackermann-ize or Not to Ackermann-ize? On Efficiently Handling Uninterpreted Function Symbols in .- Lemma Learning in the Model Evolution Calculus.