This Festschrift published in honor of Vladimir Lifschitz on the occasion of his 65th birthday presents 39 articles by colleagues from all over the world with whom Vladimir Lifschitz had cooperation in various respects. The 39 contributions reflect the breadth and the depth of the work of Vladimir Lifschitz in logic programming, circumscription, default logic, action theory, causal reasoning and answer set programming.

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.

This book constitutes the proceedings of the 19th International Symposium on Practical Aspects of Declarative Languages, PADL 2017, held in Paris, France, in January 2017 and collocated with the ACM SIGPLAN Symposium on Principles of Programming Languages. The 14 papers presented in this volume were carefully reviewed and selected from 27 submissions. They deal with novel applications and implementation techniques for all forms of declarative languages, including but not limited to logic, constraint, and functional languages.