Towards Relational Inconsistent Databases with Functional Dependencies
Lecture Notes in Computer Science, 2008
Towards Relational Inconsistent Databases with Functional Dependencies Sergio Greco andCristian M... more Towards Relational Inconsistent Databases with Functional Dependencies Sergio Greco andCristian Molinaro DEIS, Univ. ... Let DB be the following instance: emp(john, NY, admin, frank), emp(john, WA, sales, daniel), emp(mary, LA, sales, susan), emp(julie, NY, admin, frank) . ...
... ranging from the (whole) class 7 to the classes A/P and coA/7 . In this way, the ability of e... more ... ranging from the (whole) class 7 to the classes A/P and coA/7 . In this way, the ability of expressing A/P ... ramework for exploiting recent advances in in model-theoretic semantics for non-monotonic DATALOG, without surrendering naturalness and efficiency of stratified negation. ...
... For example, the query 〈Pst, st(X, Y )〉, where Pst is defined below, computes a spanning tree... more ... For example, the query 〈Pst, st(X, Y )〉, where Pst is defined below, computes a spanning tree of the graph G in polynomial time: ... Predicate symbols can be either extensional (ie defined by the facts of a database EDB predicate symbols) or intensional (ie defined by the rules ...
The paper presents a declarative semantics for the maintenance of integrity constraints expressed... more The paper presents a declarative semantics for the maintenance of integrity constraints expressed by means of production rules. A production rule is a special form of active rule, called active integrity constraint, whose body contains an integrity constraint (conjunction of literals which must be false) and whose head contains a disjunction of update atoms, i.e. actions to be performed if the corresponding constraints are not satisfied (i.e. are true). The paper introduces i) a formal declarative semantics allowing the computation of founded repairs, that is repairs whose actions are specified and supported by active integrity constraint, ii) an equivalent semantics obtained by rewriting production rules into disjunctive logic rules, so that repairs can be derived from the answer sets of the logic program, iii) a characterization of production rules allowing a methodology for integrity maintenance.
Proceedings of the eleventh ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems - PODS '92, 1992
Page 1. Greedy by Choice Sergio Greco Carlo Zaniolo Sumit Ganguly Universit% dells Calabria Univ... more Page 1. Greedy by Choice Sergio Greco Carlo Zaniolo Sumit Ganguly Universit% dells Calabria University of California at Los Angeles University of Texas at Austin 87030 Rende, Italy LosAngeles, CA 90024 Austin, TX 78712 sergio@mcc. com [email protected]. edu sumit@cs. ...
This paper presents an extension of disjunctive datalog (Datalog ∨ ) by nested rules. Nested rule... more This paper presents an extension of disjunctive datalog (Datalog ∨ ) by nested rules. Nested rules are (disjunctive) rules where elements of the head may be also rules. Nested rules increase the knowledge representation power of Datalog ∨ both from a theoretical and from a practical viewpoint. A number of examples show that nested rules allow to naturally model several real world situations that cannot be represented in Datalog ∨ . An in depth analysis of complexity and expressive power of the language shows that nested rules do increase the expressiveness of Datalog ∨ without implying any increase in its computational complexity.
This paper presents a technique for the optimization of bound queries over disjunctive deductive ... more This paper presents a technique for the optimization of bound queries over disjunctive deductive databases with constraints. The proposed approach is an extension of the wellknown Magic-Set technique and is well-suited for being integrated in current bottom-up (stable) model inference engines. More specifically, it is based on the exploitation of binding propagation techniques which reduce the size of the data relevant to answer the query and, consequently, reduces both the complexity of computing a single model and the number of models to be considered. The motivation of this work stems from the observation that traditional binding propagation optimization techniques for bottom-up model generator systems, simulating the goal driven evaluation of top-down engines, are only suitable for positive (disjunctive) queries, while hard problems are expressed using unstratified negation.
International Journal of Foundations of Computer Science, 1999
The critical problem of finding efficient implementations for recursive queries with bound argume... more The critical problem of finding efficient implementations for recursive queries with bound arguments offers many open challenges of practical and theoretical import. In particular, we need methods that are effective for the general case, such as non-linear programs, as well as for specialized cases, such as left-recursive linear programs. In this paper, we propose a novel approach that solves this problem for chain queries, i.e., for queries where bindings are propagated from arguments in the head to arguments in the tail of the rules, in a chain-like fashion. The method, called pushdown method, is based on the fact that each chain query can be associated with a context-free language, and that a pushdown automaton recognizing this language can be emulated by rewriting the query as a particular factorized left-linear program. The proposed method generalizes and unifies previous techniques such as the 'counting' and 'right-, left-, mixed-linear' methods. It succeeds in reducing many non-linear programs to query-equivalent linear ones.
A novel approach is proposed for ezpresaing and computing eficienily a large cla88 of problem8, i... more A novel approach is proposed for ezpresaing and computing eficienily a large cla88 of problem8, including jinding the shortest path in a graph, that were previously considered impervious to an efiient treatment in the declarative framework of logic-baaed languageu. Our approach w based on the u8e of ruin and nmx predicate having a jht-order semantica defined using mleu w"th negation in their bodien. We show that when certain monotonicity condition8 hold then (1) there ezists a total well-founded model for these progmrnn containing negation, (2) this model can be computed eflciently using a procedure called greedy fixpoint, and (3) the original program can be rewritten into a more eficient one by puuhing rnin and max predicate8 into recursion.
Query Optimization of Disjunctive Databases with Constraints through Binding Propagation
Lecture Notes in Computer Science, 2002
In this paper we present a technique for the optimization of bound queries over disjunctive deduc... more In this paper we present a technique for the optimization of bound queries over disjunctive deductive databases with constraints, i.e. rules defining properties which have to be satisfied by all instances over database schema. The technique we propose, allows the binding propagation into disjunctive queries with a set of constraints; thus, reducing the size of the data relevant to answer
Approximate Probabilistic Query Answering over Inconsistent Databases
Lecture Notes in Computer Science, 2008
The problem of managing and querying inconsistent databases has been deeply investigated in the l... more The problem of managing and querying inconsistent databases has been deeply investigated in the last few years. Most of the approaches proposed so far rely on the notion of repair (a minimal set of delete/insert operations making the database consistent) and consistent query answer (the answer to a query is given by considering the set of ‘repaired’ databases). Since the problem of consistent query answering is hard in the general case, most of the proposed techniques have an exponential complexity, although for special classes of constraints and queries the problem becomes polynomial. A second problem with most of the proposed approaches is that repairs do not take into account update operations (they consider delete and insert operations only). This paper presents a general framework where constraints consist of functional dependencies and queries may be expressed by positive relational algebra. The framework allows us to compute certain (i.e. tuples derivable from all or from none of the repaired databases) and uncertain query answers (i.e. tuples derivable from a proper not empty subset of the repaired databases). Each tuple in the answer is associated with a probability, which depends on the number of repaired databases from which the tuple can be derived. In the proposed framework, databases are repaired by means of update operations and repaired databases are stored by means of a “condensed” database, so that all the repaired databases can be derived by “expanding” the unique condensed database. A condensed database can be rewritten into a probabilistic database where each tuple is associated with an event (i.e. a boolean formula) and, thus, a probability value. The probabilistic query answer can be computed by querying the so obtained probabilistic database. As the complexity of querying probabilistic databases is #P-complete, approximate probabilistic answers which are computable in polynomial time are considered.
Querying and Repairing Inconsistent Databases Under Three-Valued Semantics
Lecture Notes in Computer Science, 2007
The problem of managing and querying inconsistent databases has been deeply investigated in the l... more The problem of managing and querying inconsistent databases has been deeply investigated in the last few years. As, in the general case, the problem of consistent query answering is hard, most of the techniques so far proposed have an exponential complexity. Moreover, polynomial techniques have been proposed only for restricted forms of constraints (e.g. functional dependencies) and queries. In this
Prioritized Active Integrity Constraints for Database Maintenance
Sistemi Evoluti per Basi di Dati, 2006
The paper presents a logic framework wherein constraints and preferences are used for database ma... more The paper presents a logic framework wherein constraints and preferences are used for database maintenance and querying. Our proposal is based on the use of a special type of integrity constraints (called Prioritized Active Integrity Constraints (PAICs)), whose body defines a constraint on data, whereas the head contains a set of partially ordered actions, which should be performed, if the
This paper presents a logic language for expressing NP search and optimization problems. Specific... more This paper presents a logic language for expressing NP search and optimization problems. Specifically, first a language obtained by extending (positive) Datalog with intuitive and efficient constructs (namely, stratified negation, constraints and exclusive disjunction) is introduced. Next, a further restricted language only using a restricted form of disjunction to define (non-deterministically) subsets (or partitions) of relations is investigated. This language,
Towards Relational Inconsistent Databases with Functional Dependencies
Lecture Notes in Computer Science, 2008
Towards Relational Inconsistent Databases with Functional Dependencies Sergio Greco andCristian M... more Towards Relational Inconsistent Databases with Functional Dependencies Sergio Greco andCristian Molinaro DEIS, Univ. ... Let DB be the following instance: emp(john, NY, admin, frank), emp(john, WA, sales, daniel), emp(mary, LA, sales, susan), emp(julie, NY, admin, frank) . ...
... ranging from the (whole) class 7 to the classes A/P and coA/7 . In this way, the ability of e... more ... ranging from the (whole) class 7 to the classes A/P and coA/7 . In this way, the ability of expressing A/P ... ramework for exploiting recent advances in in model-theoretic semantics for non-monotonic DATALOG, without surrendering naturalness and efficiency of stratified negation. ...
... For example, the query 〈Pst, st(X, Y )〉, where Pst is defined below, computes a spanning tree... more ... For example, the query 〈Pst, st(X, Y )〉, where Pst is defined below, computes a spanning tree of the graph G in polynomial time: ... Predicate symbols can be either extensional (ie defined by the facts of a database EDB predicate symbols) or intensional (ie defined by the rules ...
The paper presents a declarative semantics for the maintenance of integrity constraints expressed... more The paper presents a declarative semantics for the maintenance of integrity constraints expressed by means of production rules. A production rule is a special form of active rule, called active integrity constraint, whose body contains an integrity constraint (conjunction of literals which must be false) and whose head contains a disjunction of update atoms, i.e. actions to be performed if the corresponding constraints are not satisfied (i.e. are true). The paper introduces i) a formal declarative semantics allowing the computation of founded repairs, that is repairs whose actions are specified and supported by active integrity constraint, ii) an equivalent semantics obtained by rewriting production rules into disjunctive logic rules, so that repairs can be derived from the answer sets of the logic program, iii) a characterization of production rules allowing a methodology for integrity maintenance.
Proceedings of the eleventh ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems - PODS '92, 1992
Page 1. Greedy by Choice Sergio Greco Carlo Zaniolo Sumit Ganguly Universit% dells Calabria Univ... more Page 1. Greedy by Choice Sergio Greco Carlo Zaniolo Sumit Ganguly Universit% dells Calabria University of California at Los Angeles University of Texas at Austin 87030 Rende, Italy LosAngeles, CA 90024 Austin, TX 78712 sergio@mcc. com [email protected]. edu sumit@cs. ...
This paper presents an extension of disjunctive datalog (Datalog ∨ ) by nested rules. Nested rule... more This paper presents an extension of disjunctive datalog (Datalog ∨ ) by nested rules. Nested rules are (disjunctive) rules where elements of the head may be also rules. Nested rules increase the knowledge representation power of Datalog ∨ both from a theoretical and from a practical viewpoint. A number of examples show that nested rules allow to naturally model several real world situations that cannot be represented in Datalog ∨ . An in depth analysis of complexity and expressive power of the language shows that nested rules do increase the expressiveness of Datalog ∨ without implying any increase in its computational complexity.
This paper presents a technique for the optimization of bound queries over disjunctive deductive ... more This paper presents a technique for the optimization of bound queries over disjunctive deductive databases with constraints. The proposed approach is an extension of the wellknown Magic-Set technique and is well-suited for being integrated in current bottom-up (stable) model inference engines. More specifically, it is based on the exploitation of binding propagation techniques which reduce the size of the data relevant to answer the query and, consequently, reduces both the complexity of computing a single model and the number of models to be considered. The motivation of this work stems from the observation that traditional binding propagation optimization techniques for bottom-up model generator systems, simulating the goal driven evaluation of top-down engines, are only suitable for positive (disjunctive) queries, while hard problems are expressed using unstratified negation.
International Journal of Foundations of Computer Science, 1999
The critical problem of finding efficient implementations for recursive queries with bound argume... more The critical problem of finding efficient implementations for recursive queries with bound arguments offers many open challenges of practical and theoretical import. In particular, we need methods that are effective for the general case, such as non-linear programs, as well as for specialized cases, such as left-recursive linear programs. In this paper, we propose a novel approach that solves this problem for chain queries, i.e., for queries where bindings are propagated from arguments in the head to arguments in the tail of the rules, in a chain-like fashion. The method, called pushdown method, is based on the fact that each chain query can be associated with a context-free language, and that a pushdown automaton recognizing this language can be emulated by rewriting the query as a particular factorized left-linear program. The proposed method generalizes and unifies previous techniques such as the 'counting' and 'right-, left-, mixed-linear' methods. It succeeds in reducing many non-linear programs to query-equivalent linear ones.
A novel approach is proposed for ezpresaing and computing eficienily a large cla88 of problem8, i... more A novel approach is proposed for ezpresaing and computing eficienily a large cla88 of problem8, including jinding the shortest path in a graph, that were previously considered impervious to an efiient treatment in the declarative framework of logic-baaed languageu. Our approach w based on the u8e of ruin and nmx predicate having a jht-order semantica defined using mleu w"th negation in their bodien. We show that when certain monotonicity condition8 hold then (1) there ezists a total well-founded model for these progmrnn containing negation, (2) this model can be computed eflciently using a procedure called greedy fixpoint, and (3) the original program can be rewritten into a more eficient one by puuhing rnin and max predicate8 into recursion.
Query Optimization of Disjunctive Databases with Constraints through Binding Propagation
Lecture Notes in Computer Science, 2002
In this paper we present a technique for the optimization of bound queries over disjunctive deduc... more In this paper we present a technique for the optimization of bound queries over disjunctive deductive databases with constraints, i.e. rules defining properties which have to be satisfied by all instances over database schema. The technique we propose, allows the binding propagation into disjunctive queries with a set of constraints; thus, reducing the size of the data relevant to answer
Approximate Probabilistic Query Answering over Inconsistent Databases
Lecture Notes in Computer Science, 2008
The problem of managing and querying inconsistent databases has been deeply investigated in the l... more The problem of managing and querying inconsistent databases has been deeply investigated in the last few years. Most of the approaches proposed so far rely on the notion of repair (a minimal set of delete/insert operations making the database consistent) and consistent query answer (the answer to a query is given by considering the set of ‘repaired’ databases). Since the problem of consistent query answering is hard in the general case, most of the proposed techniques have an exponential complexity, although for special classes of constraints and queries the problem becomes polynomial. A second problem with most of the proposed approaches is that repairs do not take into account update operations (they consider delete and insert operations only). This paper presents a general framework where constraints consist of functional dependencies and queries may be expressed by positive relational algebra. The framework allows us to compute certain (i.e. tuples derivable from all or from none of the repaired databases) and uncertain query answers (i.e. tuples derivable from a proper not empty subset of the repaired databases). Each tuple in the answer is associated with a probability, which depends on the number of repaired databases from which the tuple can be derived. In the proposed framework, databases are repaired by means of update operations and repaired databases are stored by means of a “condensed” database, so that all the repaired databases can be derived by “expanding” the unique condensed database. A condensed database can be rewritten into a probabilistic database where each tuple is associated with an event (i.e. a boolean formula) and, thus, a probability value. The probabilistic query answer can be computed by querying the so obtained probabilistic database. As the complexity of querying probabilistic databases is #P-complete, approximate probabilistic answers which are computable in polynomial time are considered.
Querying and Repairing Inconsistent Databases Under Three-Valued Semantics
Lecture Notes in Computer Science, 2007
The problem of managing and querying inconsistent databases has been deeply investigated in the l... more The problem of managing and querying inconsistent databases has been deeply investigated in the last few years. As, in the general case, the problem of consistent query answering is hard, most of the techniques so far proposed have an exponential complexity. Moreover, polynomial techniques have been proposed only for restricted forms of constraints (e.g. functional dependencies) and queries. In this
Prioritized Active Integrity Constraints for Database Maintenance
Sistemi Evoluti per Basi di Dati, 2006
The paper presents a logic framework wherein constraints and preferences are used for database ma... more The paper presents a logic framework wherein constraints and preferences are used for database maintenance and querying. Our proposal is based on the use of a special type of integrity constraints (called Prioritized Active Integrity Constraints (PAICs)), whose body defines a constraint on data, whereas the head contains a set of partially ordered actions, which should be performed, if the
This paper presents a logic language for expressing NP search and optimization problems. Specific... more This paper presents a logic language for expressing NP search and optimization problems. Specifically, first a language obtained by extending (positive) Datalog with intuitive and efficient constructs (namely, stratified negation, constraints and exclusive disjunction) is introduced. Next, a further restricted language only using a restricted form of disjunction to define (non-deterministically) subsets (or partitions) of relations is investigated. This language,
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