Non-Finite Axiomatisability Results via Reductions: CSP Parallel Composition and CCS Restriction -- Operational Causality -- Necessarily Sufficient and Sufficiently Necessary -- Axiomatizing consciousness, with applications -- Symmetric Transrationals: The Data Type and the Algorithmic Degree of its Equational Theory -- A Survey of Model Learning Techniques for Recurrent Neural Networks -- Back-and-Forth in Space: On Logics and Bisimilarity in Closure Spaces -- Better Automata through Process Algebra -- Family-Based Fingerprint Analysis: A Position Paper -- What's in School? - Topic Maps for Secondary School Computer Science -- Tree-Based Adaptive Model Learning -- From Languages to Behaviors and Back -- The Quest for an Adequate Semantic Basis of Dense-Time Metric Temporal Logic -- Equivalence Checking 40 Years After: A Review of Bisimulation Tools -- Apartness and Distinguishing formulas in Using the parallel ATerm library for parallel model checking and state space generation -- ActiveAutomata Learning as Black-Box Search and Lazy Partition Refinement -- A Reconstruction of Ewens' Sampling Formula via Lists of Coins -- Rooted divergence-preserving branching bisimilarity is a congruence: a simpler proof -- Learning Language Intersections -- Runtime verification of compound components with ComMA -- A Basic Compositional Model for Spiking Neural Networks -- State Identification and Verification with Satisfaction -- A Note on the Message Complexity of Cidon's Distributed Depth-First Search Algorithm -- Minesweeper is difficult indeed!- Goodbye ioco -- Process Algebras and Flocks of Birds -- The Integration of Testing and Program Verification -- Discovering Directly-Follows Complete Petri Nets From Event Data -- Fair Must Testing for I/O Automata -- Passive automata learning: DFAs and NFAs.

This Festschrift, dedicated to Frits W. Vaandrager on the occasion of his 60th birthday, contains papers written by many of his closest collaborators. Frits has been a Professor of Informatics for Technical Applications at Radboud University Nijmegen since 1995, where his research focuses on formal methods, concurrency theory, verification, model checking, and automata learning. The volume contains contributions of colleagues, Ph.D. students, and researchers with whom Frits has collaborated and inspired, reflecting a wide spectrum of scientific interests, and demonstrating successful work at the highest levels of both theory and practice.