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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)
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)
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 updates(More)
The problem of rewriting queries using views is to iind a query expression that uses only a set of views V and is equivalent to (or maximally contained in) a given query Q. Rewriting queries using views is important for query optimization and for applications such as information integration and data warehousing. Description logics are a family of logics(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)
Scoping, naming and binding are central concepts in the deenition and understanding of programming languages. With the introduction of sophisticated data models, these issues become important for query languages as well. Additionally, the goal of integrating query and programming languages requires a common basis for their operational semantics. We ooer(More)