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37
On the Semantics of Theory Change: Arbitration between Old and New Information
 In Proceedings of the Twelfth ACM SIGACTSIGMODSIGART Symposium on Principles of Databases
, 1993
"... : Katsuno and Mendelzon divide theory change, the problem of adding new information to a logical theory, into two types: revision and update. We propose a third type of theory change: arbitration. The key idea is the following: the new information is considered neither better nor worse than the old ..."
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Cited by 54 (0 self)
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: Katsuno and Mendelzon divide theory change, the problem of adding new information to a logical theory, into two types: revision and update. We propose a third type of theory change: arbitration. The key idea is the following: the new information is considered neither better nor worse than the old information represented by the logical theory. The new information is simply one voice against a set of others already incorporated into the logical theory. From this follows that arbitration should be commutative. First we define arbitration by a set of postulates and then describe a modeltheoretic characterization of arbitration for the case of propositional logical theories. We also study weighted arbitration where different models of a theory can have different weights. 1 Introduction The problem of updating logical theories is a common fundamental concern to databases, to Artificial Intelligence [McC68, Rei92], and to belief revision [Mak85, Gar88]. It is wellknown that giving semant...
The AQUA Data Model and Algebra
, 1993
"... This paper describes a new objectoriented model and query algebra that will be used as an input language for the query optimizers that are being built as a part of the EREQ project. The model adopts a uniform view of objects and values and separates syntactic, semantic, and implementation concerns. ..."
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Cited by 39 (8 self)
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This paper describes a new objectoriented model and query algebra that will be used as an input language for the query optimizers that are being built as a part of the EREQ project. The model adopts a uniform view of objects and values and separates syntactic, semantic, and implementation concerns. The algebra addresses issues of typedefined equality and duplicate elimination as well as extensions to bulk types other than sets. 1 Introduction Recently, a great deal of work has been done on the topic of objectoriented query algebras [27, 22, 11] and the modeling of bulk types [4, 25, 19]. These proposals as well as those of other researchers on the topic have explored some of the fundamental issues and provided the starting point for the work reported here. AQUA (A QUery Algebra) is the result of a joint effort among researchers who have participated in the design of previous algebras [26, 30, 31]. AQUA has been designed to address a number of detailed modeling issues that we beli...
Fixpoint Logics, Relational Machines, and Computational Complexity
 In Structure and Complexity
, 1993
"... We establish a general connection between fixpoint logic and complexity. On one side, we have fixpoint logic, parameterized by the choices of 1storder operators (inflationary or noninflationary) and iteration constructs (deterministic, nondeterministic, or alternating). On the other side, we have t ..."
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Cited by 37 (5 self)
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We establish a general connection between fixpoint logic and complexity. On one side, we have fixpoint logic, parameterized by the choices of 1storder operators (inflationary or noninflationary) and iteration constructs (deterministic, nondeterministic, or alternating). On the other side, we have the complexity classes between P and EXPTIME. Our parameterized fixpoint logics capture the complexity classes P, NP, PSPACE, and EXPTIME, but equality is achieved only over ordered structures. There is, however, an inherent mismatch between complexity and logic  while computational devices work on encodings of problems, logic is applied directly to the underlying mathematical structures. To overcome this mismatch, we develop a theory of relational complexity, which bridges tha gap between standard complexity and fixpoint logic. On one hand, we show that questions about containments among standard complexity classes can be translated to questions about containments among relational complex...
Deterministic and NonDeterministic Stable Models
 Journal of Logic and Computation
, 1997
"... Stable models have been first introduced in the domain of total interpretations (T stable models), where the existence of multiple Tstable models for the same program provides a powerful mechanism to express nondeterminism. Stable models have been later extended to the domain of partial interpre ..."
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Cited by 26 (6 self)
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Stable models have been first introduced in the domain of total interpretations (T stable models), where the existence of multiple Tstable models for the same program provides a powerful mechanism to express nondeterminism. Stable models have been later extended to the domain of partial interpretations (Pstable models). In this paper, we show that the presence of multiple Pstable models need not be a direct manifestation of nondeterminism, for it can be instead an expression of assorted degrees of undefinedness. To separate the two factors, nondeterminism and undefinedness, this paper introduces the notion of deterministic stable models and strictly nondeterministic ones. Deterministic stable models form an interesting family, having a lattice structure where the wellfounded model serves as the bottom; the top of the lattice, the maximum deterministic stable model, resolves differences between any two Pstable models in the family. On the other hand, every two models in a fam...
Programming with Nondeterminism in Deductive Databases
 Annals of Mathematics and Artificial Intelligence
, 1997
"... This paper provides an overview of recent results on this topic with the aim of providing an introduction to the theory and practice of nondeterminism in deductive databases. In particular we (i) recall the main results linking nondeterministic constructs in database languages to the theory of dat ..."
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Cited by 25 (3 self)
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This paper provides an overview of recent results on this topic with the aim of providing an introduction to the theory and practice of nondeterminism in deductive databases. In particular we (i) recall the main results linking nondeterministic constructs in database languages to the theory of data complexity and the expressibility hierarchy of query languages (ii) provide a reasoned introduction to effective programming with nondeterministic constructs (iii) compare the usage of nondeterministic constructs in languages such as
Tractable Query Languages for Complex Object Databases
, 1995
"... The expressiveness and complexity of several calculusbased query languages for complex objects is considered. Unlike previous investigations, we are concerned with the complexity of queries on databases of complex objects, rather than flat databases. This raises new issues specific to complex objec ..."
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Cited by 24 (4 self)
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The expressiveness and complexity of several calculusbased query languages for complex objects is considered. Unlike previous investigations, we are concerned with the complexity of queries on databases of complex objects, rather than flat databases. This raises new issues specific to complex objects. For instance, it is shown that the way the database makes use of its higherorder types has direct impact on query complexity. The use of fixpoint operators is shown to yield languages wellbehaved with respect to complexity and expressiveness. In particular, an extension of the fixpoint queries to complex objects is shown to express precisely the PTIME queries, under the assumption that the database makes "full" use of all its types. Similar results involve rangerestricted queries. 1 Introduction Complex objects are increasingly part of advanced database systems. They provide the structural core of objectoriented databases. Several query languages for complex objects have been propo...
Semantics and Expressive Power of NonDeterministic Constructs in Deductive Databases
, 1996
"... this paper, ..."
DATALOG Queries with Stratified Negation and Choice: from P to D^P
, 1995
"... This paper introduces a unified solution to the problem of extending stratified DATALOG to express DBcomplexity classes ranging from P to D^P. The solution... ..."
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Cited by 17 (7 self)
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This paper introduces a unified solution to the problem of extending stratified DATALOG to express DBcomplexity classes ranging from P to D^P. The solution...
Expressive Power and Complexity of Partial Models for Disjunctive Deductive Databases
, 1999
"... This paper investigates the expressive power and complexity of partial model semantics for disjunctive deductive databases. In particular,... ..."
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Cited by 17 (7 self)
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This paper investigates the expressive power and complexity of partial model semantics for disjunctive deductive databases. In particular,...