Foundations of Software Science and Computational Structures (vol. # 3921) : 9th International Conference FOSSACS 2006 Held as Part of the Joint European Conferences on Theory and Practice of Software ETAPS 2006 Vienn Invited Talk On Finite Alphabets and Infinite Bases II: Completed and Ready Simulation Mobile Processes A Theory for Observational Fault Tolerance Smooth Orchestrators On the Relative Expressive Power of Asynchronous Communication Primitives More on Bisimulations for Higher Order  Calculus Software Science Register Allocation After Classical SSA Elimination is NP Complete A Logic of Reachable Patterns in Linked Data Structures Distributed Computation Dynamic Policy Discovery with Remote Attestation Distributed Unfolding of Petri Nets On the  Calculus Augmented with Sabotage Categorical Models A Finite Model Construction for Coalgebraic Modal Logic Presenting Functors by Operations and Equations Bigraphical Models of Context Aware Systems Processes for Adhesive Rewriting Systems Real Time and Hybrid Systems On Metric Temporal Logic and Faulty Turing Machines Denotational Semantics of Hybrid Automata Process Calculi Reversing Algebraic Process Calculi Conjunction on Processes: Full–Abstraction Via Ready–Tree Semantics Undecidability Results for Bisimilarity on Prefix Rewrite Systems Automata and Logic Propositional Dynamic Logic with Recursive Programs A Semantic Approach to Interpolation First Order and Counting Theories of  Automatic Structures Parity Games Played on Transition Graphs of One Counter Processes Domains Lambda Calculus Types Bidomains and Full Abstraction for Countable Nondeterminism An Operational Characterization of Strong Normalization On the Confluence of  Calculus with Conditional Rewriting Security Guessing Attacks and the Computational Soundness of Static Equivalence Handling exp × (and Timestamps) in Protocol Analysis Symbolic and Cryptographic Analysis of the Secure WS ReliableMessaging Scenario. This book constitutes the refereed proceedings of the 9th International Conference on Foundations of Software Science and Computation Structures FOSSACS 2006 held in Vienna Austria in March 2006 as part of ETAPS. The 28 revised full papers presented together with 1 invited paper were carefully reviewed and selected from 107 submissions. The papers are organized in topical sections on mobile processes software science distributed computation categorical models real time and hybrid systems process calculi automata and logic domains lambda calculus types and security.