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Verifying CTL Properties of Infinite State Systems by Specializing Constraint Logic Programs
, 2001
"... this paper we assume that a system makes transitions from states to states and its evolution can be formalized using a computation tree which is dened as follows. Given a system S and its initial state s 0 , the root of the computation tree for S is s 0 , and every node s i of the computation tree f ..."
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Cited by 28 (19 self)
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this paper we assume that a system makes transitions from states to states and its evolution can be formalized using a computation tree which is dened as follows. Given a system S and its initial state s 0 , the root of the computation tree for S is s 0 , and every node s i of the computation tree for S has a child node s j i there exists in S a transition from state s i to state s j , called a successor state of s i . The set of all states of a system may be nite or innite. We assume that in every system for every state s i there exists at least one successor state
Transformation Rules for Locally Stratified Constraint Logic Programs
, 2004
"... We propose a set of transformation rules for constraint logic programs with negation. We assume that every program is locally strati ed and, thus, it has a unique perfect model. We give sucient conditions which ensure that the proposed set of transformation rules preserves the perfect model of ..."
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Cited by 22 (19 self)
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We propose a set of transformation rules for constraint logic programs with negation. We assume that every program is locally strati ed and, thus, it has a unique perfect model. We give sucient conditions which ensure that the proposed set of transformation rules preserves the perfect model of the programs. Our rules extend in some respects the rules for logic programs and constraint logic programs already considered in the literature and, in particular, they include a rule for unfolding a clause with respect to a negative literal.
Verification of Sets of Infinite State Processes Using Program Transformation
, 2001
"... We present a method for the verification of safety properties of concurrent systems which consist of finite sets of infinite state processes. Systems and properties are specified by using constraint logic programs, and the inference engine for verifying properties is provided by a technique based on ..."
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Cited by 3 (0 self)
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We present a method for the verification of safety properties of concurrent systems which consist of finite sets of infinite state processes. Systems and properties are specified by using constraint logic programs, and the inference engine for verifying properties is provided by a technique based on unfold/fold program transformations. We deal with properties of finite sets of processes of arbitrary cardinality, and in order to do so, we consider constraint logic programs where the constraint theory is the Weak Monadic Second Order Theory of k Successors. Our verification method consists in transforming the programs that specify the properties of interest into equivalent programs where the truth of these properties can be checked by simple inspection in constant time. We present a strategy for guiding the application of the unfold/fold rules and realizing the transformations in a semiautomatic way.
Using Real Relaxations During Program Specialization
"... Abstract. We propose a program specialization technique for locally stratified CLP(Z) programs, that is, logic programs with linear constraints over the set Z of the integer numbers. For reasons of efficiency our technique makes use of a relaxation from integers to reals. We reformulate the familiar ..."
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Abstract. We propose a program specialization technique for locally stratified CLP(Z) programs, that is, logic programs with linear constraints over the set Z of the integer numbers. For reasons of efficiency our technique makes use of a relaxation from integers to reals. We reformulate the familiar unfold/fold transformation rules for CLP programs so that: (i) the applicability conditions of the rules are based on the satisfiability or entailment of constraints over the set R of the real numbers, and (ii) every application of the rules transforms a given program into a new program with the same perfect model constructed over Z. Then, we introduce a strategy which applies the transformation rules for specializing CLP(Z) programs with respect to a given query. Finally, we show that our specialization strategy can be applied for verifying properties of infinite state reactive systems specified by constraints over Z. 1
IOS Press Improving Reachability Analysis of Infinite State Systems by Specialization
"... Abstract. We consider infinite state reactive systems specified by using linear constraints over the integers, and we address the problem of verifying safety properties of these systems by applying reachability analysis techniques. We propose a method based on program specialization, which improves ..."
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Abstract. We consider infinite state reactive systems specified by using linear constraints over the integers, and we address the problem of verifying safety properties of these systems by applying reachability analysis techniques. We propose a method based on program specialization, which improves the effectiveness of the backward and forward reachability analyses. For backward reachability our method consists in: (i) specializing the reactive system with respect to the initial states, and then (ii) applying to the specialized system the reachability analysis that works backwards from the unsafe states. 282 F. Fioravanti, A. Pettorossi, M. Proietti, V. Senni / Improving Reachability Analysis by Specialization For reasons of efficiency, during specialization we make use of a relaxation from integers to reals. In particular, we test the satisfiability or entailment of constraints over the real numbers, while preserving the reachability properties of the reactive systems when constraints are interpreted over the integers. For forward reachability our method works as for backward reachability, except that the role of the initial states and the unsafe states are interchanged. We have implemented our method using the MAP transformation system and the ALV verification system. Through various experiments per
Hierarchical Decompositions for Visualizing Large Graphs
, 2002
"... In this thesis we study algorithmic problems related to the visualization of large graphs. We devise techniques based on hierarchical decompositions, imposed either on the graph or on its drawing. The first approach leads to considering clustered representations of graphs, where some parts are visua ..."
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In this thesis we study algorithmic problems related to the visualization of large graphs. We devise techniques based on hierarchical decompositions, imposed either on the graph or on its drawing. The first approach leads to considering clustered representations of graphs, where some parts are visualized in detail and others are collapsed into single vertices or filledin regions: this makes it possible both to maintain context and to reduce the amount of displayed information by hiding irrelevant details and uninteresting parts of the structure. The second approach leads to studying hierarchical drawings, where vertices are constrained to lie on a set of parallel lines and edges are represented as polygonal chains. In this case the graph is drawn entirely, though its visualization may not fit in the screen: the assumption behind the use of the layered convention is that drawings exceeding only the screen height facilitate tracing paths in the graph, and thus are easier to be explored than drawings exceeding both height and width.