We investigate the relationship between programming with constraints and database query languages. We show that efficient, declarative database programming can be combined with efficient constraint solving. The key intuition is that the generalization of a ground fact, or tuple, is a conjunction of constraints over a small number of variables. We describe the basic Constraint Query Language design principles and illustrate them with four classes of constraints: real polynomial inequalities, dense linear order inequalities, equalities over an infinite domain, and boolean equalities. For the analysis, we use quantifier elimination techniques from logic and the concept of data complexity from database theory. This framework is applicable to managing spatial data and can be combined with existing multidimensional searching algorithms and data structures.

One source of partial information in databases is the need to combine information from several databases. Even if each database is complete for some "world", the combined databases will not be, and answers to queries against such combined databases can only be approximated. In this paper we describe various situations in which a precise answer cannot be obtained for a query asked against multiple databases. Based on an analysis of these situations, we propose a classification of constructs that can be used to model approximations. A major goal is to obtain universality properties for these models of approximations. Universality properties suggest syntax for languages with approximations based on the operations which are naturally associated with them. We prove universality properties for most of the approximation constructs. Then we use them to design languages built around datatypes given by the approximation constructs. A straightforward approach results in langauges that have a numb...

We define formal notions of temporal domain and temporal database, and use them to survey a wide spectrum of temporal query languages. We distinguish between an abstract temporal database and its concrete representations, and accordingly between abstract and concrete temporal query languages. We also address the issue of incomplete temporal information. 1 Introduction A temporal database is a repository of temporal information. A temporal query language is any query language for temporal databases. In this paper we propose a formal notion of temporal database and use this notion in surveying a wide spectrum of temporal query languages. The need to store temporal information arises in many computer applications. Consider, for example, records of various kinds: financial [37], personnel, medical [98], or judicial. Also, monitoring data, e.g., in telecommunications network management [4] or process control, has often a temporal dimension. There has been a lot of research in temporal dat...

Selecting views to materialize is one of the most important decisions in designing a data warehouse. In this paper, we present a frame-work for analyzing the issues in selecting views to materialize so as to achieve the best com-bination of good query performance and low view maintenance. We first develop a heuristic algorithm which can provide a feasible solu-tion based on individual optimal query plans. We also map the materialized view design problem as O-l integer programming problem, whose solution can guarantee an optimal so-lution. 1

We consider automata with counters whose values are updated according to signals sent by the environment. A transition can be fired only if the values of the counters satisfy some guards (the guards of the transition). We consider guards of the form y i #y j +c i;j where y i is either x 0 i or x i , the values of the counter i respectively after and before the transition, and # is any relational symbol in f=; ; ; ?; !g. We show that the set of possible counter values which can be reached after any number of iterations of a loop is definable in the additive theory of N (or Z or R depending on the type of the counters). This result can be used for the safety analysis of multiple counters automata. 1 Introduction Finite state automata provide a nice framework for the verification of reactive systems. Their main advantage is the equivalence between recognizability and definability in some decidable logic (e.g. Monadic Second Order Logic or some of its fragments such as tempora...

. The declarative programming paradigms used in constraint languages can lead to powerful extensions of Codd's relational data model. The development of constraint database query languages from logical database query languages has many similarities with the development of constraint logic programming from logic programming, but with the additional requirements of data efficient, set-at-a-time, and bottomup evaluation. In this overview of constraint query languages (CQLs) we first present the framework of [41]. The principal idea is that: "the k-tuple (or record) data type can be generalized by a conjunction of quantifier-free constraints over k variables". The generalization must preserve various language properties of the relational data model, e.g., the calculus/algebra equivalence, and have time complexity polynomial in the size of the data. We next present an algebra for dense order constraints that is simpler to evaluate than the calculus described in [41], and we sharpen some of...

We survey a number of approaches to the problem of finite representation of infinite temporal extensions. Two of them, Datalog 1S and Templog, are syntactical extensions of Datalog; the third is based on repetition and arithmetic constraints. We provide precise characterizations of the expressiveness and the computational complexity of these languages. We also describe query evaluation methods.

: We study classes of infinite but finitely representable databases based on constraints, motivated by new database applications such as geographical databases. We formally define these notions and introduce the concept of query which generalizes queries over classical relational databases. We prove that in this context the basic properties of queries (satisfiability, containment, equivalence, etc.) are nonrecursive. We investigate the theory of finitely representable models and prove that it differs strongly from both classical model theory and finite model theory. In particular, we show that most of the well known theorems of either one fail (compactness, completeness, locality, 0/1 laws, etc.). An immediate consequence is the lack of tools to consider the definability of queries in the relational calculus over finitely representable databases. We illustrate this very challenging problem through some classical examples. We then mainly concentrate on dense order databases, and exhibit...

this paper, we present a procedure that generates and propagates minimum QRP-constraints (if it terminates), based on the definition and uses of program predicates (Section 4). By propagating minimum QRP-constraints to the original program, we obtain a program that fully utilizes the constraint information present in the original program. This procedure is based on two sub-procedures: 1. Procedure Gen Prop predicate-constraints, which generates and propagates constraints that are satisfied by program predicates based on their definitions.

In recent years, much work has been directed towards evaluating logic programs and queries on deductive databases by using an iterative bottom-up fixpoint computation. The resulting techniques offer an attractive alternative to Prolog-style top-down evaluation in several situations. They are sound and complete for positive Horn clause programs, are well-suited to applications with large volumes of data (facts), and can support a variety of extensions to the standard logic programming paradigm. We present the basics of database query evaluation and logic programming evaluation, and then discuss bottom-up fixpoint evaluation. We discuss an approach based upon using a program transformation ("Magic Templates") to restrict search, followed by fixpoint computation using a technique ("Semi-naive evaluation") that avoids repeated inferences. The program transformation technique focuses the fixpoint evaluation, which is a forward-chaining strategy, by propagating bindings in the goal in a ma...