This book constitutes the refereed proceedings of the 14th International Conference on Logic Programming and Nonmonotonic Reasoning, LPNMR 2017, held in Espoo, Finland, in July 2017. The 16 full papers and 11 short papers presented in this volume were carefully reviewed and selected from 47 submissions. The book also contains 4 invited talks. The papers were organized in topical sections named: nonmonotonic reasoning; answer set programming; LPNMR systems; and LPNMR applications.

This Festschrift volume, published in honor of Michael Gelfond on the occasion of his 65th birthday, contains a collection of papers written by his closest friends and colleagues. Several of these papers were presented during the Symposium on Constructive Mathematics in Computer Science, held in Lexington, KY, USA on October 25-26, 2010.

The 27 scientific papers included in the book focus on answer set programming. The papers are organized in sections named Foundations: ASP and Theories of LP, KR, and NMR, ASP and Dynamic Domains, and ASP Applications and Tools ."

This book constitutes the refereed proceedings of the 15th International Conference on Logic Programming and Nonmonotonic Reasoning, LPNMR 2019, held in Philadelphia, PA, USA, in June 2019.The 22 full papers and 3 short papers presented in this volume were carefully reviewed and selected from a total of 39 submissions. The papers were organized in topical sections named: applications; argumentation; foundations and complexity; knowledge representation and reasoning; and systems.