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A class of database schemes, called acychc, was recently introduced. It is shown that this class has a number of desirable properties. In particular, several desirable properties that have been studied by other researchers m very different terms are all shown to be eqmvalent to acydicity. In addition, several equivalent charactenzauons of the class m termsâ€¦ (More)

This paper considers the efficient evaluation of recursive queries expressed using Horn Clauses. We define <italic>sideways information passing</italic> formally and show how a query evaluation algorithm may be defined in terms of sideways information passing and control. We then consider a class of information passing strategies which suffices to describeâ€¦ (More)

A class of dependencies, tuple and equality generating dependencies, is defined, and the chase process is generalized to deal with these dependenetes. For total dependencies the chase is an exponential ttme decision procedure for the implication problem, and in some restricted cases it can be modified to run m polynomial Ume. For nontotal dependencies theâ€¦ (More)

We investigate the inference rules that can be applied to functional and multivalued dependencies that exist in a database relation. Three types of rules are discussed. First, we list the well known rules for functional dependencies. Then we investigate the rules for multivalued dependencies. It is shown that for each rule for functional dependencies theâ€¦ (More)

Answering queries in a relational database often requires that the natural join of two or more relations be computed. However, the result of a join may not be what one expects. In this paper we give efficient algorithms to determine whether the join of several relations has the intuitively expected value (is <italic>lossless</italic>) and to determineâ€¦ (More)

There is a class of database descriptions, involving one “acyclic” join dependency and a collection of functional dependencies, and nothing else, that appears powerful enough to describe most any real-world body of data in relational database terms. Further, this class has many desirable properties. Some properties make operations like updatesâ€¦ (More)

Today's standard model for database concurrency control, called serializability theory, represents executions of transactions as partial orders of operations. The theory tells when an execution is serializable, that is, when the set of operations of a transaction execute atomically with respect to those of other transactions. It has been used successfullyâ€¦ (More)

An Armstrong relation for a set of functional dependencies (FDs) is a relation that satisfies each FD implied by the set but no FD that is not implied by it. The structure and size (number of tuples) of Armstrong relatsons are investigated. Upper and lower bounds on the size of minimal-sized Armstrong relations are derived, and upper and lower bounds on theâ€¦ (More)

The problem of whether a given dependency in a database relation can be derived from a given set of dependencies is investigated. We show that the problem can be decided in polynomial time when the given set consists of either multivalued dependencies only or of both functional and multivalued dependencies and the given dependency is also either aâ€¦ (More)

In this paper we extend LDL, a Logic Based Database Language, to include finite sets and negation. The new language is called LDL1. We define the notion of a model and show that a negation-free program need not have a model, and that it may have more than one minimal model. We impose syntactic restriction in order to define a deterministic language. Theseâ€¦ (More)