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Logics for unranked trees: an overview
 Logical Methods in Computer Science 2, Issue 3, Paper 2
, 2006
"... Vol. 2 (3:2) 2006, pp. 1–31 www.lmcsonline.org ..."
Recurrent reachability analysis in regular model checking
 In LPAR’08
"... Abstract. We consider the problem of recurrent reachability over infinite systems given by regular relations on words and trees, i.e, whether a given regular set of states can be reached infinitely often from a given initial state in the given transition system. Under the condition that the transiti ..."
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Abstract. We consider the problem of recurrent reachability over infinite systems given by regular relations on words and trees, i.e, whether a given regular set of states can be reached infinitely often from a given initial state in the given transition system. Under the condition that the transitive closure of the transition relation is regular, we show that the problem is decidable, and the set of all initial states satisfying the property is regular. Moreover, our algorithm constructs an automaton for this set in polynomial time, assuming that a transducer of the transitive closure can be computed in polytime. We then demonstrate that transition systems generated by pushdown systems, regular ground tree rewrite systems, and the wellknown process algebra PA satisfy our condition and transducers for their transitive closures can be computed in polytime. Our result also implies that model checking EFlogic extended by recurrent reachability predicate (EGF) over such systems is decidable. 1
Queries on Xml Streams with Bounded Delay and Concurrency
"... Streaming algorithms for Xml query answering call for efficient memory management. Tractable queries are distinguished by a bounded number of concurrently alive answer candidates at every time point, and a bounded delay for node selection, for every candidate. We show that both properties are decida ..."
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Streaming algorithms for Xml query answering call for efficient memory management. Tractable queries are distinguished by a bounded number of concurrently alive answer candidates at every time point, and a bounded delay for node selection, for every candidate. We show that both properties are decidable in polynomial time for queries defined by deterministic tree automata. Our results are obtained by reduction to the bounded valuedness problem for recognizable relations between unranked trees, a problem that we show to be decidable in polynomial time. Key words: streaming, tree automata, Xml, databases. 1.
Regular Languages of Nested Words: Fixed Points, Automata, and Synchronization
"... Nested words provide a natural model of runs of programs with recursive procedure calls. The usual connection between monadic secondorder logic (MSO) and automata extends from words to nested words and gives us a natural notion of regular languages of nested words. In this paper we look at some wel ..."
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Nested words provide a natural model of runs of programs with recursive procedure calls. The usual connection between monadic secondorder logic (MSO) and automata extends from words to nested words and gives us a natural notion of regular languages of nested words. In this paper we look at some wellknown aspects of regular languages – their characterization via fixed points, deterministic and alternating automata for them, and synchronization for defining regular relations – and extend them to nested words. We show that mucalculus is as expressive as MSO over finite and infinite nested words, and the equivalence holds, more generally, for mucalculus with past modalities evaluated in arbitrary positions in a word, not only in the first position. We introduce the notion of alternating automata for nested words, show that they are as expressive as the usual automata, and also prove that Muller automata can be determinized (unlike in the case of visibly pushdown languages). Finally we look at synchronization over nested words. We show that the usual lettertoletter synchronization is completely incompatible with nested words (in the sense that even the weakest form of it leads to an undecidable formalism) and present an alternative form of synchronization that gives us decidable notions of regular relations.
Hyperset Approach to Semistructured Databases Computation of Bisimulation in the Distributed Case
"... Abstract. We will briefly describe the recently implemented hyperset approach to semistructured or Weblike and possibly distributed databases with the query system available online at ..."
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Abstract. We will briefly describe the recently implemented hyperset approach to semistructured or Weblike and possibly distributed databases with the query system available online at
Logics with counting: Very Challenging Presentation Topics
, 2010
"... Here is a list of very challenging topics which you might like to give a presentation on for the course Logics with Counting. They are in no particular order. All of the topics can be done (more or less successfully) by anyone who has followed the course; and none of them lacks the potential for doi ..."
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Here is a list of very challenging topics which you might like to give a presentation on for the course Logics with Counting. They are in no particular order. All of the topics can be done (more or less successfully) by anyone who has followed the course; and none of them lacks the potential for doing serious and challenging work. Note also that these are only suggestions. If you have a better idea, then I’d be happy to hear about it. I have provided a few bibliographic suggestions to get you started. These are not intended to be definitive. If this is too daunting, don’t worry! It is perfectly acceptable to pick a topic that I have discussed in class, and give your own presentation on it. I realize that you have other courses to take and lives to get on with.... 1. Suppose we are given a finite set of formulas of propositional logic, together with a probability assignment to each formula, for example: P(p1∧¬p2) = 0.6, P(p2 → (¬p4 ∨ p1)) = 0.72,.... How do we decide whether such an assignment is coherent, according to the usual laws of probability theory?