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This book constitutes the refereed proceedings of the 15th International Colloquium on Theoretical Aspects of Computing, ICTAC 2018, held in Stellenbosch, South Africa, in October 2018.

The 25 revised full papers presented together with two short and two long invited talks were carefully reviewed and selected from 59 submissions.

The ICTAC conference aims at bringing together researchers and practitioners from academia, industry and government to present research and exchange ideas and experience addressing challenges in both theoretical aspects of computing and the exploitation of theory through methods and tools for system development. ICTAC also specifically aims to promote research cooperation between developing and industrial countries.

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Formal Verification of a Geometry Algorithm: A Quest for Abstract Views and Symmetry in Coq Proofs.- LTL Semantic Tableaux and Alternating Omega-automata via Linear Factors.- Proof Nets and the Linear Substitution Calculus.- Modular Design of Domain-Specific Languages Using Splittings of Catamorphisms.- An Automata-Based View on Configurability and Uncertainty.- Formalising Boost POSIX Regular Expression Matching.- Monoidal Multiplexing.- Input/Output Stochastic Automata with Urgency: Conuence and Weak Determinism.- Layer by Layer: Combining Monads.- Layer Systems for Confluence - Formalized.- A Metalanguage for Guarded Iteration.- Generating Armstrong ABoxes for ALC TBoxes.- Spatio-Temporal Domains: An Overview.- Checking Modal Contracts for Virtually Timed Ambients.- Abstraction of Bit-Vector Operations for BDD-Based SMT Solvers.- Weak Bisimulation Metrics in Models with Nondeterminism and Continuous State Spaces.- Symbolic Computation via Program Transformation.- Double Applicative Functors.- Checking Sequence Generation for Symbolic Input/Output FSMs by Constraint Solving.- Explicit Auditing.- Complexity and Expressivity of Branching- and Alternating-Time Temporal Logics with Finitely Many Variables.- Complexity Results on Register Context-Free Grammars and Register Tree Automata.- Information Flow Certificates.- The Smallest FSSP Partial Solutions for One-Dimensional Ring Cellular Automata: Symmetric and Asymmetric Synchronizers.- Convex Language Semantics for Nondeterministic Probabilistic Automata.- Fast Computations on Ordered Nominal Sets.- Non-preemptive Semantics for Data-Race-Free Programs.

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