The 9th Italian Conference on Theoretical Computer Science (ICTCS 2005)was held at the Certosa di Pontignano, Siena, Italy, on October 12 14 2005. The Certosa di Pontignano is the conference center of the University of Siena; it is located 8 km away from the town and it is in the Chianti region. The Certosa is a place full of history (founded in the 15th century, it was set on ?re a century later and reconstructed) and of valuable artworks, like frescoes of the Scuola Senese. Previous conferences took place in Pisa (1972), Mantova (1974 and 1989), L Aquila(1992),Ravello(1995),Prato(1998),Turin(2001)andBertinoro(2003). Theconferenceaimsatbringingtogethercomputerscientists,especiallyyoung researchers, to foster cooperation, exchange of ideas and results. Great e?orts have been made to attract researchers from all over the world. The main t- ics of the conference cover all the ?elds of theoretical computer science and include analysis and design of algorithms, computability, computational c- plexity, cryptography, formal languages and automata, foundations of progr- ming languages and program analysis, foundations of arti?cial intelligence and knowledge representation, foundations of web programming, natural computing paradigms (quantum computing, bioinformatics), parallel and distributed c- putation, program speci?cation and veri?cation, term rewriting, theory of c- currency, theory of data bases, theory of logical design and layout, type theory, security, and symbolic and algebraic computation.

Inhalt
Invited Contributions.- Semantic Subtyping: Challenges, Perspectives, and Open Problems.- Biological Systems as Reactive Systems.- Mobile Agents Computing: Security Issues and Algorithmic Solutions.- Technical Contributions.- Efficient Algorithms for Detecting Regular Point Configurations.- Pickup and Delivery for Moving Objects on Broken Lines.- A Static Analysis of PKI-Based Systems.- Subtyping Object and Recursive Types Logically.- The Language ?: Circuits, Computations and Classical Logic.- Checking Risky Events Is Enough for Local Policies.- The Graph Rewriting Calculus: Confluence and Expressiveness.- Safe Object Composition in the Presence of Subtyping.- Reachability Analysis in Boxed Ambients.- Error Mining for Regular Expression Patterns.- Reconstructing an Alternate Periodical Binary Matrix from Its Orthogonal Projections.- Inapproximability Results for the Lateral Gene Transfer Problem.- Faster Deterministic Wakeup in Multiple Access Channels.- Weighted Coloring: Further Complexity and Approximability Results.- Quantum Algorithms for a Set of Group Theoretic Problems.- On the Computational Complexity of the L (2,1)-Labeling Problem for Regular Graphs.- A Polymerase Based Algorithm for SAT.- Laxity Helps in Broadcast Scheduling.- Enforcing and Defying Associativity, Commutativity, Totality, and Strong Noninvertibility for One-Way Functions in Complexity Theory.- Synthesis from Temporal Specifications Using Preferred Answer Set Programming.- Model Checking Strategic Abilities of Agents Under Incomplete Information.- Improved Algorithms for Polynomial-Time Decay and Time-Decay with Additive Error.- A Theoretical Analysis of Alignment and Edit Problems for Trees.- A Complete Formulation of Generalized Affine Equivalence.- A New Combinatorial Approach to SequenceComparison.- A Typed Assembly Language for Non-interference.- Improved Exact Exponential Algorithms for Vertex Bipartization and Other Problems.- A Typed Semantics of Higher-Order Store and Subtyping.- Two Variables Are Not Enough.