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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 terms(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 the(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 describe(More)
There is a class of database descriptions, involving one &#8220;acyclic&#8221; 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 updates(More)
3 This article summarizes mathematical formalisms used to describe object and object-oriented databases. Different approaches were used to describe object databases, object database models respectively. We focus on algebraic approaches including graphs, monoid comprehensions, monads and semi-monads, and applied type theory. Especially we introduce formal(More)
19 are valid in a given relation instance R do follow from a given cover F is coN P-complete. Finally, we have analyzed several conditions under which the main problems become polynomially solvable. One relevant problem remains open: given a relation instance R and a cover F of FDs, what is the complexity of deciding whether F R = F + ? This problem is(More)
Problems related to functional dependencies and the algorithmic design of relational schemas are examined. Specifically, the following results are presented: (1) a tree model of derivations of functional dependencies from other functional dependencies; (2) a linear-time algorithm to test if a functional dependency is in the closure of a set of functional(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 a(More)