A data model, called the entity-relationship model, is proposed. This model incorporates some of the important semantic information about the real world. A special diagrammatic technique is introduced as a tool for database design. An example of database design and description using the model and the diagrammatic technique is given. Some implications for data integrity, infor-mation retrieval, and data manipulation are discussed. The entity-relationship model can be used as a basis for unification of different views of data: t,he network model, the relational model, and the entity set model. Semantic ambiguities in these models are analyzed. Possible ways to derive their views of data from the entity-relationship model are presented. Key Words and Phrases: database design, logical view of data, semantics of data, data models, entity-relationship model, relational model, Data Base Task Group, network model, entity set

A new type of dependency, which includes the well-known functional dependencies as a special case, is defined for relational databases. By using this concept, a new (“fourth”) normal form for relation schemata is defined. This fourth normal form is strictly stronger than Codd’s “im-proved third normal form ” (or “Boyce-Codd normal form”). It is shown that, every relation schema can be decomposed into a family of relation schemata in fourth normal form without loss of information (that is, the original relation can be obtained from the new relations by taking joins). Key words and phrases: database design, multivalued dependency, functional dependency, fourth normal form, 4NF, third normal form, 3NF, Boyce-Codd normal form, normalization, decomposition, relational database

A multiuser database system must selectively permit users to share data, while retaining the ability to restrict data access. There must be a mechanism to provide protection and security, permitting information to be accessed only by properly authorized users. Further, when tables or restricted views of tables are created and destroyed dynamically, the granting, authentica-tion, and revocation of authorization to use them must also be dynamic. Each of these issues and their solutions in the context of the relational database management system System R are discussed. When a database user creates a table, he is fully and solely authorized to perform upon it actions such as read, insert, update, and delete. He may explicitly grant to any other user any or all of his privileges on the table. In addition he may specify that that user is authorized to further grant these privileges to still other users. The result is a directed graph of granted pri-vileges originating from the table creator. At some later time a user A may revoke some or all of the privileges which he previously granted to another user B. This action usually revokes the entire subgraph of the grants ori-ginating from A’s grant to B. It may be, however, that B will still possess the revoked privi-leges by means of a grant from another user C, and therefore some or all of B’s grants should not be revoked. This problem is discussed in detail, and an algorithm for detecting exactly which of B’s grants should be revoked is presented.

permission from the publisher. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. © 2000 IEEE. Copyright and all rights therein are retained by authors or by other copyright holders. All persons downloading this information are expected to adhere to the terms and constraints invoked by copyright. This document or any part thereof may not be reposted without the explicit permission of the copyright holder. Citation for this copy: Levene, Mark and Vincent, Millist W. (2000) Justification for inclusion dependency normal form. London: Birkbeck ePrints. Available at:

Since the beginnings of the relational model, it was clear for the database community that the process of designing a database is a nontrivial and timeconsuming

A key is simple if it consists of a single attribute. It is shown that if a relation schema is in third normal form and every key is simple, then it is in projection-join normal form (sometimes called fifth normal form), the ultimate normal form with respect to projections and joins. Furthermore, it is shown that if a relation schema is in Boyce-Codd normal form and some key is simple, then it is in fourth normal form (but not necessarily projection-join normal form). These results give the database designer simple sufficient conditions, defined in terms of functional dependencies alone, that guarantee that the schema being designed is automatically in higher normal forms.

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The conjecture "Transitive Property is not applicable to Functional Dependence (FD)" has been developed in three aspects: 1) In 3NF context, the term Non-key Dependence describes the problem better than Transitive Dependence. 3NF procedure is not affected by the existence (or not) of Transitive Property.

Abstract. We present a new approach to virtual, object-oriented, updateable views in object databases. Within this approach it is possible to include into a view definition information on user intents of view updates. These information have a form of procedures that overload default update operations performed on virtual objects. Due to procedures we support full algorithmic power of view definitions, which is essential for many applications. The proposed mechanism is based on the Stack- Based Approach to query languages in which query language is treated as a special kind of programming language and is operated in the similar manner. 1

Normalization as a way of producing good database designs is a well understood topic for relational data. In this paper we discuss the problem of eliminating redundancies and preserving data dependencies in XML data when an XML schema is normalized. Normalization is one of the main tasks in relational database design, where 3NF or BCNF, is to be reached. However, neither of them is ideal: 3NF preserves dependencies but may not always eliminate redundancies, BCNF on the contrary – always eliminates redundancies but may not preserve constraints. In this paper we consider the possibility of achieving both redundancy-free and dependency preserving form of XML schema. We show how the XML normal form can be obtained for a class of XML schemas and a class of XML functional dependencies. We relate our approach to the decomposition algorithm proposed by Arenas and Libkin in [1]. Povzetek: Razvita je metoda pretvorbe XML podatkov v normalizirano obliko s poudarkom na odstranjevanju redundanc. 1