ETAPS 2001 was the fourth instance of the European Joint Conferences on Theory and Practice of Software. ETAPS is an annual federated conference that was established in 1998 by combining a number of existing and new conferences. This year it comprised ve conferences (FOSSACS, FASE, ESOP, CC, TACAS), ten satellite workshops (CMCS, ETI Day, JOSES, LDTA, MMAABS, PFM, RelMiS, UNIGRA, WADT, WTUML), seven invited lectures, a debate, and ten tutorials. The events that comprise ETAPS address various aspects of the system de- lopment process, including speci cation, design, implementation, analysis, and improvement. The languages, methodologies, and tools which support these - tivities are all well within its scope. Di erent blends of theory and practice are represented, with an inclination towards theory with a practical motivation on one hand and soundly-based practice on the other. Many of the issues involved in software design apply to systems in general, including hardware systems, and the emphasis on software is not intended to be exclusive.

InhaltsangabeA Query Language Based on the Ambient Logic.- Probabilistic Polynomial-Time Process Calculus and Security Protocol Analysis.- A Systematic Approach to Static Access Control.- Secure Information Flow and CPS.- Enforcing Safety Properties Using Type Specialization.- Semantics and Program Analysis of Computationally Secure Information Flow.- Encoding Intensional Type Analysis.- Fusion on Languages.- Programming the Web with High-Level Programming Languages.- On the Completeness of Model Checking.- Modal Transition Systems: A Foundation for Three-Valued Program Analysis.- Entailment with Conditional Equality Constraints.- On the Complexity of Constant Propagation.- What Are Polymorphically-Typed Ambients?.- JOIN(X): Constraint-Based Type Inference for the Join-Calculus.- Modular Causality in a Synchronous Stream Language.- Control-Flow Analysis in Cubic Time.- The Recursive Record Semantics of Objects Revisited.- A Formalisation of Java's Exception Mechanism.- A Formal Executable Semantics of the JavaCard Platform.- Modeling an Algebraic Stepper.- Typestate Checking of Machine Code.- Proof-Directed De-compilation of Low-Level Code.- Backwards Abstract Interpretation of Probabilistic Programs.- Tool Demonstration: Finding Duplicated Code Using Program Dependences.- Compiling Problem Specifications into SAT.- Semantics and Termination of Simply-Moded Logic Programs with Dynamic Scheduling.- The Def-inite Approach to Dependency Analysis.