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Complexity and Expressive Power of Logic Programming
, 1997
"... This paper surveys various complexity results on different forms of logic programming. The main focus is on decidable forms of logic programming, in particular, propositional logic programming and datalog, but we also mention general logic programming with function symbols. Next to classical results ..."
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Cited by 287 (57 self)
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This paper surveys various complexity results on different forms of logic programming. The main focus is on decidable forms of logic programming, in particular, propositional logic programming and datalog, but we also mention general logic programming with function symbols. Next to classical results on plain logic programming (pure Horn clause programs), more recent results on various important extensions of logic programming are surveyed. These include logic programming with different forms of negation, disjunctive logic programming, logic programming with equality, and constraint logic programming. The complexity of the unification problem is also addressed.
GraphLog: a Visual Formalism for Real Life Recursion
 In Proceedings of the Ninth ACM SIGACTSIGMOD Symposium on Principles of Database Systems
, 1990
"... We present a query language called GraphLog, based on a graph representation of both data and queries. Queries are graph patterns. Edges in queries represent edges or paths in the database. Regular expressions are used to qualify these paths. We characterize the expressive power of the language a ..."
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Cited by 168 (18 self)
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We present a query language called GraphLog, based on a graph representation of both data and queries. Queries are graph patterns. Edges in queries represent edges or paths in the database. Regular expressions are used to qualify these paths. We characterize the expressive power of the language and show that it is equivalent to stratified linear Datalog, first order logic with transitive closure, and nondeterministic logarithmic space (assuming ordering on the domain). The fact that the latter three classes coincide was not previously known. We show how GraphLog can be extended to incorporate aggregates and path summarization, and describe briefly our current prototype implementation. 1 Introduction The literature on theoretical and computational aspects of deductive databases, and the additional power they provide in defining and querying data, has grown rapidly in recent years. Much less work has gone into the design of languages and interfaces that make this additional pow...
Diagnosis of Asynchronous Discrete Event Systems: Datalog to the Rescue!
 IN ACM PODS
, 2005
"... We consider query optimization techniques for data intensive P2P applications. We show how to adapt an old technique from deductive databases, namely QuerySubQuery (QSQ), to a setting where autonomous and distributed peers share large volumes of interelated data. We illustrate the technique with a ..."
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Cited by 32 (12 self)
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We consider query optimization techniques for data intensive P2P applications. We show how to adapt an old technique from deductive databases, namely QuerySubQuery (QSQ), to a setting where autonomous and distributed peers share large volumes of interelated data. We illustrate the technique with an important telecommunication problem, the diagnosis of distributed telecom systems. We show that (i) the problem can be modeled using Datalog programs, and (ii) it can benefit from the large battery of optimization techniques developed for Datalog. In particular, we show that a simple generic use of the extension of QSQ achieves an optimization as good as that previously provided by dedicated diagnosis algorithms. Furthermore, we show that it allows solving efficiently a much larger class of system analysis problems.
Semantical Characterizations and Complexity of Equivalences in Answer Set Programming
 ACM TRANSACTIONS ON COMPUTATIONAL LOGIC
, 2007
"... In recent research on nonmonotonic logic programming, repeatedly strong equivalence of logic programs P and Q has been considered, which holds if the programs P ∪ R and Q ∪ R have the same answer sets for any other program R. This property strengthens the equivalence of P and Q with respect to answe ..."
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Cited by 28 (12 self)
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In recent research on nonmonotonic logic programming, repeatedly strong equivalence of logic programs P and Q has been considered, which holds if the programs P ∪ R and Q ∪ R have the same answer sets for any other program R. This property strengthens the equivalence of P and Q with respect to answer sets (which is the particular case for R =∅), and has its applications in program optimization, verification, and modular logic programming. In this article, we consider more liberal notions of strong equivalence, in which the actual form of R may be syntactically restricted. On the one hand, we consider uniform equivalence where R is a set of facts, rather than a set of rules. This notion, which is wellknown in the area of deductive databases, is particularly useful for assessing whether programs P and Q are equivalent as components of a logic program which is modularly structured. On the other hand, we consider relativized notions of equivalence where R ranges over rules over a fixed alphabet, and thus generalize our results to relativized notions of strong and uniform equivalence. For all these notions, we consider disjunctive logic programs in the propositional (ground) case as well as some restricted classes, providing semantical characterizations and analyzing the computational complexity. Our results, which naturally extend to answer set semantics for programs with strong negation, complement the results on strong
The Expressiveness of a Family of Finite Set Languages
 IN PROCEEDINGS OF 10TH ACM SYMPOSIUM ON PRINCIPLES OF DATABASE SYSTEMS
, 1991
"... In this paper we characterise exactly the complexity of a set based database language called SRL, which presents a unified framework for queries and updates. By imposing simple syntactic restrictions on it, we are able to express exactly the classes, P and LOGSPACE. We also discuss the role of orde ..."
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Cited by 26 (3 self)
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In this paper we characterise exactly the complexity of a set based database language called SRL, which presents a unified framework for queries and updates. By imposing simple syntactic restrictions on it, we are able to express exactly the classes, P and LOGSPACE. We also discuss the role of ordering in database query languages and show that the hom operator of Machiavelli language in [OBB89] does not capture all the orderindependent properties.
A Time Bound on the Materialization of Some Recursively Defined Views 385 [Ioan] [Lewi] [Mink] [Naug] [Reit] [Sagi 1] [Sagi 2] [Ston] [Viei
, 1985
"... Abstract. A virtual relation (or view) can be defined with a recursive Horn clause that is a function of one or more base relations. In general, the number of times such a Horn clause must be applied in order to retrieve all the tuples in the virtual relation depends on the contents of the base rela ..."
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Cited by 11 (0 self)
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Abstract. A virtual relation (or view) can be defined with a recursive Horn clause that is a function of one or more base relations. In general, the number of times such a Horn clause must be applied in order to retrieve all the tuples in the virtual relation depends on the contents of the base relations of the definition. However, there exist Horn clauses for which there is an upper bound on the number of applications ecessary toform the virtual relation, independent of the contents of the base relations. Considering a restricted class of recursive Horn clauses, we give necessary and sufficient conditions for members of the class to have this bound.
Evaluating Recursive Queries in Distributed Databases
 IEEE Transactions on Knowledge and Data Engineering
, 1993
"... In this paper, we study the execution of logic queries in a distributed database environment. We assume that each local database system can execute logic queries, and we design methods for the efficient execution of queries requiring data from multiple sites. Conventional optimization strategies ..."
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Cited by 8 (1 self)
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In this paper, we study the execution of logic queries in a distributed database environment. We assume that each local database system can execute logic queries, and we design methods for the efficient execution of queries requiring data from multiple sites. Conventional optimization strategies which are wellknown in the field of distributed databases, such as the early evaluation of selection conditions and the clustering of processing to manipulate and exchange large sets of tuples, are redefined in view of the additional difficulties due to logic queries, in particular to recursive rules. In order to allow efficient processing of these logic queries we present several program transformation techniques which attempt to minimize distribution costs based on the idea of semijoins and generalized semijoins in conventional databases. Although local computation of semijoins is not possible for the general case, we indicate classes of programs for which these transformation...
On Transformations into Linear Database Logic Programs
 Perspectives of Systems Informatics, 2nd International Andrei Ershov Memorial Conference, Akademgorodik
, 1996
"... Abstract. We consider the problem of transformations of logic programs without function symbols (database logic programs) into a special subclass, namely linear logic programs. Linear logic programs are dened to be the programs whose rules have at most one intentional atom in their bodies. a) We inv ..."
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Cited by 6 (5 self)
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Abstract. We consider the problem of transformations of logic programs without function symbols (database logic programs) into a special subclass, namely linear logic programs. Linear logic programs are dened to be the programs whose rules have at most one intentional atom in their bodies. a) We investigate linearizability of several syntactically de ned subclasses of programs and present both positive and negative results (i.e. demonstrate programs that cannot be transformed into a linear program by any transformation technique), and b) We develop an algorithm which transforms any program in a speci c subclass namely the piecewise logic programs into a linear logic program.
Complexity and Composition of Synthesized Web Services
, 2008
"... The paper investigates fundamental decision problems and composition synthesis for Web services commonly found in practice. We propose a notion of synthesized Web services (SWS’s) to specify the behaviors of the services. Upon receiving a sequence of input messages, an SWS issues multiple queries to ..."
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Cited by 5 (1 self)
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The paper investigates fundamental decision problems and composition synthesis for Web services commonly found in practice. We propose a notion of synthesized Web services (SWS’s) to specify the behaviors of the services. Upon receiving a sequence of input messages, an SWS issues multiple queries to a database and generates actions, in parallel; it produces external messages and database updates by synthesizing the actions parallelly generated. In contrast to previous models for Web services, SWS’s advocate parallel processing and (deterministic) synthesis of actions. We classify SWS’s based on what queries an SWS can issue, how the synthesis of actions is expressed, and whether unbounded input sequences are allowed in a single interaction session. We show that the behaviors of Web services supported by various prior models, datadriven or not, can be specified by different SWS classes. For each of these classes we study the nonemptiness, validation and equivalence problems, and establish matching upper and lower bounds on these problems. We also provide complexity bounds on composition synthesis for these SWS classes, identifying decidable cases.
DATALOG SIRUPs Uniform Boundedness Is Undecidable
, 1996
"... DATALOG is the paradigmatic database query language. If it is possible to eliminate recursion from a DATALOG program then it is uniformly bounded. Since uniformly bounded programs can be executed in parallel constant time, the possibility of automatized boundedness detection is an important issue, ..."
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Cited by 1 (0 self)
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DATALOG is the paradigmatic database query language. If it is possible to eliminate recursion from a DATALOG program then it is uniformly bounded. Since uniformly bounded programs can be executed in parallel constant time, the possibility of automatized boundedness detection is an important issue, and has been studied in many papers. In this paper we solve one of the most famous open problems in the theory of deductive databases ( see eg. P.C. Kanellakis, Elements of Relational Database Theory in Handbook of Theoretical Computer Science) showing that uniform boundedness is undecidable for single rule programs (called also sirups). 1 Introduction 1.1 Introduction The query relation R, that answers, for a given directed graph (database), if it is possible, for given two nodes, to reach one of them from the other in an odd number of steps, is not a first order one. That is because of the lack of recursion in the first order logic. This observation led to the study of DATALOG (DATAbase LO...