This book constitutes the thoroughly refereed post-workshop proceedings of the 5th International Workshop on Declarative Agent Languages and Technologies, DALT 2007, held in Honolulu, USA, in 2007. It was an associated event of AAMAS 2007, the conference on autonomous agents and multi-agent systems. The 11 full papers, together with 1 keynote lecture and 2 invited papers from the AAMAS main conference were carefully selected and substantially enhanced after the workshop.

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."