Ibtissem Ben Makhlouf and Sarah Winter: Presentation of their work

Ibtissem Ben Makhlouf: Reachability Analysis of Hybrid Systems Using Geometric Approximations

Hybrid systems combine discrete events and continuous behaviors in the same framework. The discrete part is represented as transitions between locations, in which the continuous part is described as a differential equation and that generally in a confined invariant domain. The transitions are commonly triggered if a related guard condition is fulfilled. After an eventually reset condition, the hybrid automaton springs to the next location if its invariant condition is met.

The reachability analysis consists in computing all states reached by a hybrid automaton when starting with an initial set or under uncertainties in the input.

In this talk, I will give an overview on methods for computing reachable sets of linear time-invariant hybrid systems.  I will particularly focus on techniques based on set mapping theory and geometric set approximations.

Sarah Winter: Synthesis of Deterministic Top-down Tree Transducers from Automatic Tree Relations

We consider the synthesis of deterministic tree transducers from automaton definable specifications, given as binary relations, over finite trees. We consider the case of specifications that are deterministic top-down tree automatic, meaning the specification is recognizable by a deterministic top-down tree automaton that reads the two given trees synchronously in parallel. In this setting we study tree transducers that are allowed to have either bounded delay or arbitrary delay.Delay is caused whenever the transducer reads a symbol from the input tree but does not produce output.

We provide decision procedures for both bounded and arbitrary delay that yield deterministic top-down tree transducers which realize the specification for valid input trees.Similar to the case of relations over words, we use two-player games to obtain our results.

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