Reachability Problems

The Third International Workshop on Reachability Problems, RP 2009 was held in Ecole Polytechnique, September 23-25, 2009, in Palaiseau, near to Paris, France. Reachability Problems 2009 was hosted as an edition of the annual LIX Fall Colloquium. The LIX Fall Colloquium is the annual colloquium organized by the computer science laboratory of Ecole Polytechnique. The topics of this c- loquiumchange everyyear. Previouseditions includeEmerging Trends in Visual Computing (ETVC 2008) in 2008,Complex Industrial Systems: Modeling, Ve- ?cationandOptimization in2007,and Emerging TrendsinConcurrencyTheory in 2006. TheReachabilityProblemsworkshopsseriesaimsatgatheringtogethersch- ars from diverse disciplines and backgrounds interested in reachability problems that appear inalgebraicstructures,computationalmodels,hybridsystems,ve- ?cation,etc. Reachabilityis afundamentalprobleminthe contextofmanym- els and abstractions which describe various computational processes. Analysis of the computational traces and predictability questions for such models can be formalized as a set of di?erent reachability problems. In general reachability can be formulated as follows: Given a computational system with a set of allowed transformations (functions), decide whether a certain state of a system is rea- able from a given initial state by a set of allowed transformations. The same questions can be asked not only about reachability of exact states of the system but also about a set of states expressed in term of some property as a pa- meterized reachability problem. Another set of predictability questions can be seen in terms of reachability of eligible traces of computations; unavoidability of some dynamics and a possibility to avoid undesirable dynamics using a limited control.