Graph-Classes of Argumentation Frameworks with Collective Attacks -- Introducing a Tool for Concurrent Argumentation -- Probabilistic Argumentation: an Approach Based on Conditional Probability - a Preliminary Report -- Conditional Descriptor Revision and its Implementation by a CSP -- Trust is All You Need: From Belief Revision to Information Revision -- Computing Defeasible Meta-Logic -- Syntax Splitting for Iterated Contractions, Ignorations, and Revisions Using Selection Strategies -- An Epistemic Logic for Multi-Agent Systems with Budget and Costs -- Epistemic Reasoning About Rationality and Bids in Auction -- Tractable Combinations of Theories via Sampling -- Analyzing Refutability of Difference Constraint Systems in Selected Refutation Systems -- Residuation for Lexicographic Orders -- Exploiting forwardness: Satisfiability and Query-Entailment in Forward Guarded Fragment -- An Algebraic View on p-Admissible Concrete Domains for Lightweight Description Logics -- ReAD: AD-Based Modular Ontology Classification -- Weighted Defeasible Knowledge Bases and a Multipreference Semantics for a Deep Neural Network Model -- A Computationally Grounded Logic of Graded Belief -- Tractability Frontiers in Probabilistic Team Semantics and Existential Second-Order Logic Over the Reals -- An Epistemic Probabilistic Logic With Conditional Probabilities -- On Syntactic Forgetting under Uniform Equivalence -- Solving a Multi-Resource Partial-Ordering Flexible Variant of the Job-Shop Scheduling Problem with Hybrid ASP -- Tractable Reasoning Using Logic Programs with Intensional Concepts -- Estimating Grounding Sizes of Logic Programs under Answer Set Semantics and System Predictor -- Testing in ASP: Revisited Language and Programming Environment -- An Abstract View on Optimizations in SAT and ASP -- Model Reconciliation in Logic Programs -- Lazy Stream Manipulation in Prolog via Backtracking: the Case of 2P-Kt -- Transforming Gringo Rules Into Formulas in a Natural Way -- DualGrounder: Lazy Instantiation via Clingo Multi-Shot Framework -- A Multi-shot ASP Encoding for the Aircraft Routing and Maintenance Planning Problem.

This book constitutes the proceedings of the 17th European Conference on Logics in Artificial Intelligence, JELIA 2021, held as a virtual event, in May 2021. The 27 full papers and 3 short papers included in this volume were carefully reviewed and selected from 68 submissions. The accepted papers span a number of areas within Logics in AI, including: argumentation; belief revision; reasoning about actions, causality, and change; constraint satisfaction; description logics and ontological reasoning; non-classical logics; and logic programming (answer set programming).