The three-volume set LNCS 12476 - 12478 constitutes the refereed proceedings of the 9th International Symposium on Leveraging Applications of Formal Methods, ISoLA 2020, which was planned to take place during October 20–30, 2020, on Rhodes, Greece.

Automating Software Re-Engineering (Introduction to the ISoLA 2020 Track).- Formal Verification of Developer Tests: a Research Agenda Inspired by Mutation Testing.- Modular Regression Verification for Reactive Systems.- Finding Idioms in Source Code using Subtree Counting Techniques.- Parametric Timed Bisimulation.- A Unifying Framework for Dynamic Monitoring and a Taxonomy of Optimizations.- Thirty-seven years of relational Hoare logic: remarks on its principles and history.- Safer Parallelization.- Refactoring and Active Object Languages.- Rigorous Engineering of Collective Adaptive Systems  --  Introduction to the 3rd Track Edition.- Composition of Component Models - a Key to Construct Big Systems.- Degrees of Autonomy in Coordinating Collectives of Self-Driving Vehicles.- Engineering semantic self-composition of services through tuple-based coordination.- A Dynamic Logic for Systems with Predicate-based Communication.- Behavioural Abstractions for Collective AdaptiveSystems.- Verifying AbC specifications via emulation.- Adaptive Security Policies.- Capturing Dynamicity and Uncertainty in Security and Trust via Situational Patterns.- Guaranteeing Type Consistency in Collective Adaptive Systems.- Epistemic Logic in Ensemble Specification.- FScaFi: a Core Calculus for Collective Adaptive Systems Programming.- Writing Robotics Applications with X-Klaim.- Measuring Adaptability and Reliability of Large Scaled Systems.- Centrality-preserving exact reductions of Multi-Layer Networks.- Towards Dynamic Dependable Systems through Evidence-Based Continuous Certification.- Forming Ensembles at Runtime: A Machine Learning Approach.- Synthesizing Control for a System with Black Box Environment, based on Deep Learning.- A Formal Model For Reasoning About The Ideal Fitness In Evolutionary Processes.- A case study of policy synthesis for swarm robotics..- Maple-Swarm: Programming Collective Behavior for Ensembles by extending HTN-Planning.- Swarm and Collective Capabilities for Multipotent Robot Ensembles.