Tagging schemes have been used in security protocols to ensure that the analysis of such protocols can work with messages of bounded length. When the set of nonces is bounded, this leads to decidability of secrecy. In this paper, we show that tagging schemes can be used to obtain decidability of secrecy even in the presence of unbound-

We study a decidable fixpoint extension of temporal description logics. To this end we employ and extend decidability results obtained for various temporally first-order monodic extensions of (firstorder) description logics. Using these techniques we obtain decidability and tight complexity results for various fixpoint extensions of temporal description logics.

Two-way alternating automata on trees were introduced by Vardi [Va98]. Here we consider alternating two-way automata on graphs and show the decidability of the following problem: ,,does a given automaton with the Büchi condition accept any finite graph?” Using this result we demonstrate the decidability of the finite model problem for a certain fragment of the modal μ-calculus with backward mod...

We prove a general decidability result for a class of intuitionistic modal logics. The proof is a slight modification of the Ganzinger, Meyer and Veanes [6] result on decidability of the two variable monadic guarded fragment of first order logic with constraints on the guard relations expressible in monadic second order logic.

We consider the decidability of existence of solutions to language equations involving the operations of shuffle and deletion along trajectories. These operations generalize the operations of concatenation, insertion, shuffle, quotient, sequential and scattered deletion, as well as many others. Our results are constructive in the sense that if a solution exists, it can be effectively represente...

We introduce different extensions of LTL where propositional variables are replaced by constraints interpreted in Z. We show different decidability and complexity results for the satisfiability and model checking problems of these logics. The extension of LTL over a wide set of qualitative constraints is shown to be pspace-complete. When introducing some quantitative constraints, we must consid...