This book constitutes the refereed proceedings of the 12th European Symposium on Programming, ESOP 2003, held in Warsaw, Poland, in April 2003.The 25 revised full papers presented together with two invited papers were carefully reviewed and selected from 99 submissions.

Invited Talks.- Computer Security from a Programming Language and Static Analysis Perspective.- What Makes a Cryptographic Protocol Secure? The Evolution of Requirements Specification in Formal Cryptographic Protocol Analysis.- Contributed Papers.- A Tail-Recursive Semantics for Stack Inspections.- Flexible Models for Dynamic Linking.- Correction of Functional Logic Programs.- Approximate Pruning in Tabled Logic Programming.- Goal-Independent Suspension Analysis for Logic Programs with Dynamic Scheduling.- Security Properties: Two Agents Are Sufficient.- A Simple Language for Real-Time Cryptographic Protocol Analysis.- Rule Formats for Non Interference.- On the Secure Implementation of Security Protocols.- Handling Encryption in an Analysis for Secure Information Flow.- Using Controller-Synthesis Techniques to Build Property-Enforcing Layers.- Automatic Software Model Checking Using CLP.- Verifying Temporal Heap Properties Specified via Evolution Logic.- Correctness of Data Representations Involving Heap Data Structures.- Modeling Web Interactions.- Type Inference for a Distributed ?-Calculus.- Type-Safe Update Programming.- Type Error Slicing in Implicitly Typed Higher-Order Languages.- Core Formal Molecular Biology.- Requirements on the Execution of Kahn Process Networks.- Tagging, Encoding, and Jones Optimality.- The Rely-Guarantee Method in Isabelle/HOL.- Building Certified Libraries for PCC: Dynamic Storage Allocation.- Finite Differencing of Logical Formulas for Static Analysis.- Register Allocation by Proof Transformation.