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31
An Access Control Model Supporting Periodicity Constraints and Temporal Reasoning
 ACM Transactions on Database Systems
, 1998
"... this paper, we present an access control model in which periodic temporal intervals are associated with authorizations. An authorization is automatically granted in the specified intervals and revoked when such intervals expire. Deductive temporal rules with periodicity and order constraints are pro ..."
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Cited by 92 (17 self)
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this paper, we present an access control model in which periodic temporal intervals are associated with authorizations. An authorization is automatically granted in the specified intervals and revoked when such intervals expire. Deductive temporal rules with periodicity and order constraints are provided to derive new authorizations based on the presence or absence of other authorizations in specific periods of time. We provide a solution to the problem of ensuring the uniqueness of the global set of valid authorizations derivable at each instant, and we propose an algorithm to compute this set. Moreover, we address issues related to the efficiency of access control by adopting a materialization approach. The resulting model provides a high degree of flexibility and supports the specification of several protection requirements that cannot be expressed in traditional access control models.
Parameterized verification of infinitestate processes with global conditions
 In Proc. 19Ø�Int. Conf. on Computer Aided Verification
"... Abstract. We present a simple and effective approximated backward reachability algorithm for parameterized systems with existentially and universally quantified global conditions. The individual processes operate on unbounded local variables ranging over the natural numbers. In addition, processes m ..."
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Cited by 36 (10 self)
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Abstract. We present a simple and effective approximated backward reachability algorithm for parameterized systems with existentially and universally quantified global conditions. The individual processes operate on unbounded local variables ranging over the natural numbers. In addition, processes may communicate via broadcast, rendezvous and shared variables. We apply the algorithm to verify mutual exclusion for complex protocols such as Lamport’s bakery algorithm both with and without atomicity conditions, a distributed version of the bakery algorithm, and RicartAgrawala’s distributed mutual exclusion algorithm. 1
Datalog with Integer Periodicity Constraints
 Proc. 1994 International Logic Programming Symposium
, 1994
"... This paper introduces a generalization of Datalog based on the notion of integer periodicity constraints. A closed form evaluation procedure running in PTIME for this class of constraints is developed. The periodicity constraints are then combined with integer (gap)order constraints and an evaluati ..."
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Cited by 33 (9 self)
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This paper introduces a generalization of Datalog based on the notion of integer periodicity constraints. A closed form evaluation procedure running in PTIME for this class of constraints is developed. The periodicity constraints are then combined with integer (gap)order constraints and an evaluation procedure for the combination is developed. A general method for combining different classes of constraints in the framework of Datalog is also discussed. 1 Introduction Generalized databases [1, 10, 12] are infinite databases that can be represented using finite sets of generalized (or constraint) tuples. A number of query languages over such databases have been studied. The proposed query languages differ with respect to: ffl the underlying inference mechanism (first order vs. deductive) ffl the constraint language used. In this paper we study generalized Datalog programs (functionfree logic programs) that operate on constraint tuples in the place of ground atoms. This idea comes fr...
The Complexity of Query Evaluation in Indefinite Temporal Constraint Databases
 Theoretical Computer Science
, 1997
"... In previous work we have developed the scheme of indefinite Lconstraint databases where L, the parameter, is a firstorder constraint language. This scheme extends the constraint database proposal of Kanellakis, Kuper and Revesz to include indefinite (or uncertain) information in the style of Imiel ..."
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Cited by 27 (11 self)
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In previous work we have developed the scheme of indefinite Lconstraint databases where L, the parameter, is a firstorder constraint language. This scheme extends the constraint database proposal of Kanellakis, Kuper and Revesz to include indefinite (or uncertain) information in the style of Imielinski and Lipski. In this paper we study the complexity of query evaluation in an important instance of this abstract scheme: indefinite temporal constraint databases. Our results indicate that the data/combined complexity of query evaluation does not change when we move from queries in relational calculus over relational databases, to queries in relational calculus with temporal constraints over temporal constraint databases. This fact remains true even when we consider query evaluation in relational databases with indefinite information vs. query evaluation in indefinite temporal constraint databases. In the course of our work, we provide precise bounds on the complexity of decision/quanti...
Constraint Databases: A Survey
 Semantics in Databases, number 1358 in LNCS
, 1998
"... . Constraint databases generalize relational databases by finitely representable infinite relations. This paper surveys the state of the art in constraint databases: known results, remaining open problems and current research directions. The paper also describes a new algebra for databases with inte ..."
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Cited by 25 (3 self)
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. Constraint databases generalize relational databases by finitely representable infinite relations. This paper surveys the state of the art in constraint databases: known results, remaining open problems and current research directions. The paper also describes a new algebra for databases with integer order constraints and a complexity analysis of evaluating queries in this algebra. In memory of Paris C. Kanellakis 1 Introduction There is a growing interest in recent years among database researchers in constraint databases, which are a generalization of relational databases by finitely representable infinite relations. Constraint databases are parametrized by the type of constraint domains and constraint used. The good news is that for many parameters constraint databases leave intact most of the fundamental assumptions of the relational database framework proposed by Codd. In particular, 1. Constraint databases can be queried by constraint query languages that (a) have a semantics ba...
Datalog queries of set constraint databases
 In Proceedings of the International Conference on Database Theory
, 1995
"... Abstract. Extension of the relational database model to represent complex data has been a focus of much research in recent years. At the same time, an alternative extension of the relational database model has proposed using constraint databases that finitely describe infinite relations. This paper ..."
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Cited by 21 (7 self)
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Abstract. Extension of the relational database model to represent complex data has been a focus of much research in recent years. At the same time, an alternative extension of the relational database model has proposed using constraint databases that finitely describe infinite relations. This paper attempts to combine these two divergent approaches. In particular a query language called Datalog with set order constraints, or Datalog ⊂ P(Z) , is proposed. This language can express many natural problems with sets, including reasoning about inheritance hierarchies. Datalog ⊂ P(Z) queries over set constraint databases are shown to be evaluable bottomup in closed form and to have DEXPTIMEcomplete data complexity. 1
DISCO: A Constraint Database System with Sets
 In CONTESSA Workshop on Constraint Databases and Applications
, 1995
"... . This paper describes the implementation of a constraint database system with integer and set of integers data types. The system called DISCO allows Datalog queries and input databases with both integer gaporder [30] and set order constraints [31]. The DISCO query language can easily express many ..."
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Cited by 18 (8 self)
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. This paper describes the implementation of a constraint database system with integer and set of integers data types. The system called DISCO allows Datalog queries and input databases with both integer gaporder [30] and set order constraints [31]. The DISCO query language can easily express many complex problems involving sets. The paper also presents efficient running times for several sample queries. 1 Introduction Recently there has been much interest in constraint databases that generalize relational databases by allowing infinite relations that are finitely represented using constraint tuples (ex., [23, 3, 4, 8, 17, 21, 25, 28]). DISCO (short for Datalog with Integer and Set order COnstraints) is a constraint database system being developed at the University of Nebraska. DISCO implements a particular case of constraint query languages for which a general framework was proposed in [23] analogously to the constraint logic programming framework of Jaffar and Lassez [18]. The part...
Safe Stratified Datalog with Integer Order Programs
 In International Conference on Constraint Programming
, 1995
"... . Guaranteeing termination of programs on all valid inputs is important for database applications. Termination cannot be guaranteed in Stratified Datalog with integer (gap)order, or Datalog :;! Z , programs on generalized databases because they can express any Turingcomputable function [23]. This ..."
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Cited by 17 (4 self)
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. Guaranteeing termination of programs on all valid inputs is important for database applications. Termination cannot be guaranteed in Stratified Datalog with integer (gap)order, or Datalog :;! Z , programs on generalized databases because they can express any Turingcomputable function [23]. This paper introduces a restriction of Datalog :;! Z that can express only computable queries. The restricted language has a high expressive power and a nonelementary data complexity. 1 Introduction Constraint logic programming [14, 15, 27, 12, 10, 9] has a great potential for being adapted for database use. A successful adaptation of constraint logic programming has to meet usual database requirements. In the constraint query languages framework [19] two requirements are identified as especially important: (a) closedform evaluation and (b) bottomup processing. Closedform evaluation means that all possible tuple answers to a query are represented finitely by an output constraint database ...
Handling Parameterized Systems with NonAtomic Global Conditions
"... We consider verification of safety properties for parameterized systems with linear topologies. A process in the system is an extended automaton, where the transitions are guarded by both local and global conditions. The global conditions are nonatomic, i.e., a process allows arbitrary interleaving ..."
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Cited by 13 (8 self)
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We consider verification of safety properties for parameterized systems with linear topologies. A process in the system is an extended automaton, where the transitions are guarded by both local and global conditions. The global conditions are nonatomic, i.e., a process allows arbitrary interleavings with other transitions while checking the states of all (or some) of the other processes. We translate the problem into model checking of infinite transition systems where each configuration is a labeled finite graph. We derive an overapproximation of the induced transition system, which leads to a symbolic scheme for analyzing safety properties. We have implemented a prototype and run it on several nontrivial case studies, namely nonatomic versions of Burn’s protocol, Dijkstra’s protocol, the Bakery algorithm, Lamport’s distributed mutual exclusion protocol, and a twophase commit protocol used for handling transactions in distributed systems. As far as we know, these protocols have not previously been verified in a fully automated framework. 1
Descriptive Complexity Theory for Constraint Databases
 IN COMPUTER SCIENCE LOGIC, NUMBER 1683 IN LNCS
, 1999
"... We consider the data complexity of various logics on two important classes of constraint databases: dense order and linear constraint databases. For dense order databases, we present a general result allowing us to lift results on logics capturing complexity classes from the class of finite orde ..."
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Cited by 9 (3 self)
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We consider the data complexity of various logics on two important classes of constraint databases: dense order and linear constraint databases. For dense order databases, we present a general result allowing us to lift results on logics capturing complexity classes from the class of finite ordered databases to dense order constraint databases. Considering linear constraints, we show that there is a significant gap between the data complexity of firstorder queries on linear constraint databases over the real and the natural numbers. This is done by proving that for arbitrary high levels of the Presburger arithmetic there are complete firstorder queries on databases over (N; !; +). The proof of the theorem demonstrates a simple argument for translating complexity results for prefix classes in logical theories to results on the complexity of query evaluation in constraint databases.