This book constitutes the proceedings of the 21st International Conference on Formal Engineering Methods, ICFEM 2019, held in Shenzhen, China, in November 2019.

Secure Deep Learning Engineering: a Road towards Quality Assurance of Intelligent Systems.- Using DimSpec for Bounded and Unbounded Software Model Checking.- SMTBCF: Efficient Backbone Computing for SMT Formulas.- Automatic verification for node-based visual script notation using model checking.- A Reo Model of Software Defined Networks.- Design of point-and-click user interfaces for proof assistants.- SqlSol: An accurate SQL Query Synthesizer.- Towards Verifying Ethereum Smart Contracts at Intermediate Language Level.- Simulations for ATL with imperfect information.- On the generation of equational dynamic logics for weighted imperative programs.- A Security Calculus for Wireless Networks of Named Data Networking.- Automatic Modularization of Large Programs for Bounded Model Checking.- PDNet: A Programming Language for Software-Defined Networks with VLAN.- Consistency Enforcement for Static First-Order Invariants in Sequential Abstract State Machines.- Probably Approximate Safety Verification of Hybrid Dynamical Systems.- A Formally Verified Algebraic Approach for Dynamic Reliability Block Diagrams.- Reasoning about Universal Cubes in MCMT.- sCompile: Critical Path Identification and Analysis for Smart Contracts.- A Mechanized Theory of Program Refinement.- A Relational Static Semantics for Call Graph Construction.- Solution Enumeration Abstraction - A Modeling Idiom to Enhance a Lightweight Formal Method.- Formal Analysis of Qualitative Long-Term Behaviour in Parametrised Boolean Networks.- Combining Parallel Emptiness Checks with Partial Order Reductions.- A Coalgebraic Semantics Framework for Quantum Systems.- Parameterized Hardware Verification Through A Term-level Generalized Symbolic Trajectory Evaluation.- An Axiomatisation of the Probabilistic -Calculus.- Synthesizing Nested Ranking Functions for Loop Programs via SVM.- A First Step in the Translation of Alloy to Coq.- Assessment of a Formal Requirements Modeling Approach on a Transportation System.- Design Model Repair with Formal Verification.- A Performance-Sensitive Malware Detection System on Mobile Platform.- Certifying Hardware Model Checking Results.- A Note on Failure Mode Reasoning.- Robustness of Piece-wise Linear Neural Network with Feasible Region Approaches.- Formal Specification and Verification of Smart Contracts.- Spatio-Temporal Specification Language for Cyber-Physical Systems.- A Modeling Framework of Cyber-Physical-Social Systems with Human Behavior Classification based on Machine Learning.