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This open access book constitutes the proceedings of the 22nd International Conference on Foundations of Software Science and Computational Structures, FOSSACS 2019, which took place in Prague, Czech Republic, in April 2019, held as part of the European Joint Conference on Theory and Practice of Software, ETAPS 2019. The 29 papers presented in this volume were carefully reviewed and selected from 85 submissions. They deal with foundational research with a clear significance for software science.

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Universal Graphs and Good for Small Games Automata: New Tools for Infinite Duration Games.- Resource-Tracking Concurrent Games.- Change Actions: Models of Generalised Differentiation.- Coalgebra Learning via Duality.- Tight Worst-Case Bounds for Polynomial Loop Programs.- A Complete Normal-Form Bisimilarity for State.- Identifiers in Registers - Describing Network Algorithms with Logic.- The Impatient May Use Limited Optimism to Minimize Regret.- Causality in Linear Logic: Full Completeness and Injectivity (Unit-Free Multiplicative-Additive Fragment).- Rewriting Abstract Structures: Materialization Explained Categorically.- Two-Way Parikh Automata with a Visibly Pushdown Stack.- Kleene Algebra with Hypotheses.- Trees in Partial Higher Dimensional Automata.- The Bernays-Schoenfinkel-Ramsey Class of Separation Logic on Arbitrary Domains.- Continuous Reachability for Unordered Data Petri Nets is in PTime.- Optimal Satisfiability Checking for Arithmetic mu-Calculi.- Constructing Inductive-Inductive Types in Cubical Type Theory.- Causal Inference by String Diagram Surgery.- Higher-Order Distributions for Differential Linear Logic.- Languages Ordered by the Subword Order.- Strong Adequacy and Untyped Full-Abstraction for Probabilistic Coherence Spaces.- A Sound and Complete Logic for Algebraic Effects.- Equational Axiomatization of Algebras with Structure.- Towards a Structural Proof Theory of Probabilistic mi-Calculi.- Partial and Conditional Expectations in Markov Decision Processes with Integer Weights.- Equational Theories and Monads from Polynomial Cayley Representations.- A Dialectica-Like Interpretation of a Linear MSO on Infinite Words.- Deciding Equivalence of Separated Non-Nested Attribute Systems in Polynomial Time.- Justness: A Completeness Criterion for Capturing Liveness Properties.- Path category for Free - Open Morphisms from Coalgebras with Non-Deterministic Branching.

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