Framework design of a domain-key schema of a relational database
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FRAMEWORK DESIGN OF A DOMAIN-KEY SCHEMA OF A RELATIONAL DATABASE UDC 004.652
B. E. Panchenko
Abstract. A new approach to the synthesis of the domain-key normal form (DK/NF) for an arbitrary domain is proposed. The Cartesian dependency, which is a special case of multivalued dependencies, is investigated. A lemma on the non-abnormality of a special relational and a theorem on the non-abnormality of the actual part of a relational framework are proved. A new criterion for determining the belonging of a database schema to DK/NF is given. The proposed approach can be used in designing information warehouse schemas. Keywords: relational database schema, relational framework, domain-key normal form (DK/NF), arbitrary object domain, synthesis of a DK/NF schema. INTRODUCTION In developing applications and synthesizing database (DB) schemas modelling different object domains (ObDs) within the framework of the classical relational data model (RDB), data structures arise, and it is common practice to simplify them. In [1], the following list of such structures is presented: relationships of the type F : H, n-ary and recursive relationships between entities-objects, attributes of relationships, hierarchical dependencies (“weakness”) between entities-objects, multiple attributes, and also one more important problem concerning not so much database design as the database maintenance, i.e., the modifiability of a relational schema, is discussed. As is well known, in the course of time, any DB schema that does satisfy new requirements should be updated, which usually significantly increases maintenance costs. Therefore, frequent redesigns of a DB schema leads to reengineering of applications, which is undesirable for users in view of large temporal and financial expenditures. Therefore, the modifiability of a DB schema becomes one of the most important quality criteria of an application. The concept of “modifiability” as a significant quality factor of a DB schema was first introduced in [2] and was partially formalized in [3]. In these works, the modifiability of a DB schema is understood as the addition of new subschemas (to) or elimination of existing subschemas from the DB and also a modification of the schema of any relation that does not affect other relations. An algorithm for synthesizing modified DB schemas is also proposed, and the significance of the property of modifiability of a DB schema for application maintenance is shown. The hypothesis that the greatest possible degree of modifiability is provided only by a DB schema represented in domain-key normal form (DK/NF) [5] was first formulated in [4]. But in [4] and later on, the author did not properly formalize this hypothesis, the algorithm is not rigorously substantiated, and the synthesis procedure is not unique and complete. The DB schema obtained as a result of solution of the described problems must finally satisfy the crossplatformness and interoperability criteria [6]. “Crossplatformness” is understood to be the independency of applications on both hardware a
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