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TQL: A Query Language for Semistructured Data Based on the Ambient Logic
 Mathematical Structures in Computer Science
, 2003
"... this paper we present TQL, a query language for semistructured data that is based on the ambient logic ..."
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this paper we present TQL, a query language for semistructured data that is based on the ambient logic
A Modal Perspective on Path Constraints
, 2003
"... We analyze several classes of path constraints for semistructured data and prove a umber of decidability and complexity results for such constraints. While some of our decidability results were known before, we believe that our improved complexity bounds are new. Our proofs are based on technique ..."
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We analyze several classes of path constraints for semistructured data and prove a umber of decidability and complexity results for such constraints. While some of our decidability results were known before, we believe that our improved complexity bounds are new. Our proofs are based on techniques from modal logic and automata theory. We believe that our modal logic perspective sheds additional light on the reasons for previously known decidability and complexity results.
Efficient Fragment of Transitive Closure Logic
, 1999
"... We define a fragment of FO 2 (TC) (with boolean variables) that admits efficient model checking  linear time with a small constant  as a function of the size of structure being checked. The fragment is expressive enough so that modal logics PDL and CTL ? can be linearly embedded in it. 1 Int ..."
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We define a fragment of FO 2 (TC) (with boolean variables) that admits efficient model checking  linear time with a small constant  as a function of the size of structure being checked. The fragment is expressive enough so that modal logics PDL and CTL ? can be linearly embedded in it. 1 Introduction Many problems that we want to solve in computer science are equivalent to the graph reachability problem, REACH: given a large, directed graph G = (V; E) with two specified vertices s; t, is there a path in G from s to t. In particular most problems in computeraided verification and in query evaluation for semistructured data can be reduced to REACH. For this reason, an elegant and expressive language for expressing such problems is FO(TC)  firstorder logic with the addition of a transitive closure operator. In [IV97] an efficient translation is given from the expressive model checking language CTL ? to the twovariable fragment FO 2 (TC). In [AdR] a large set of path co...
Fast Stream  Efficient Fragments of Transitive Closure Logic
"... ble, making it suitable for many applications which involve analysing graphs. Complexity of query evaluation and decidability Given a set of FO or FO(TC) formulas, e.g. `every web page is reachable from this page', `this web page contains no links' we can ask: Evaluation are these formulas true fo ..."
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ble, making it suitable for many applications which involve analysing graphs. Complexity of query evaluation and decidability Given a set of FO or FO(TC) formulas, e.g. `every web page is reachable from this page', `this web page contains no links' we can ask: Evaluation are these formulas true for the given data (or: which tuples satisfy these formulas)? Decidability are these formulas consistent (or: do they imply some other formula) ? The rst question is asked when evaluating a database query or checking whether a circuit design satises some property (model checking). FO and FO(TC) queries can be evaluated in polynomial time. For large graphs (verifying properties of the World Wide Web, for example) more ecient query evaluation procedures are needed. 1 The second question is asked when checking whether some set of constraints is consistent or deriving consequences from the data. There is no algorithm for answering this q