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MAPPING CONSIDERATIONS IN THE DESIG~ OF SCHEMAS FOR THE RELATIONAL MODEL

IP.com Disclosure Number: IPCOM000128156D
Original Publication Date: 1979-Dec-31
Included in the Prior Art Database: 2005-Sep-15
Document File: 35 page(s) / 75K

Publishing Venue

Software Patent Institute

Related People

Sabah Al-Fedaghi: AUTHOR [+4]

Abstract

The tpical design process for the relational database model develops the conceptual schema and each of the external schemas separately and independei,-.ly from each other. This paper proposes a new design meth-odology th,,t constructs the conceptual schema in such a way that over-lappings among external schemas are reflected. If the overlappings of external schemas do not produce transitivity at the conceptual level, then with our design method, the relations in the external schemas can be realized as a join over independent components. Thus a one-to-one function can be defined for the mapping between tuples in the external schemas to tuples in the conceptual schema. If transitivity is produced, then we show that no such function is possible and a new technique is introduced to handle this special case. index Terms: relational database mode, logical database design, conceptual schema, external schema, interferences, mapping functions, functional dependencies, independent components.

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Page 1 of 35

THIS DOCUMENT IS AN APPROXIMATE REPRESENTATION OF THE ORIGINAL.

MAPPING CONSIDERATIONS IN THE DESIG~ OF SCHEMAS FOR THE RELATIONAL MODEL

Sabah Al-Fedaghi and Peter Scheuermann Department of Electrical Engineering and Computer Science Northwestern University Evanston, Illinois 60201

No. 79-05-DBM-04

R00W

COMPUTER SCIENCE DEPARTMERT YALE UNjVF8SfTY

* This work is sponsored in part by NSF Grant NCS77-03904.

ABSTRACT

The tpical design process for the relational database model develops the conceptual schema and each of the external schemas separately and independei,-.ly from each other. This paper proposes a new design meth-odology th,,t constructs the conceptual schema in such a way that over-lappings among external schemas are reflected. If the overlappings of external schemas do not produce transitivity at the conceptual level, then with our design method, the relations in the external schemas can be realized as a join over independent components. Thus a one-to- one function can be defined for the mapping between tuples in the external schemas to tuples in the conceptual schema. If transitivity is produced, then we show that no such function is possible and a new technique is introduced to handle this special case.

index Terms: relational database mode, logical database design, conceptual schema, external schema, interferences, mapping functions, functional dependencies, independent components.

1. Introduction

In the relational database model, a given external view, V k and the. conceptual view, V, are~described I by sets of relations. The set of rela-tions in the conceptual view.constitutes the conceptual schema and the set of relations in a given external view constitutes an external schema. Given a relational model let

(Equation Omitted)

be the set of the external schemas and C be the conceptual schema of the model. The mapping problem covers several transformations between a given E k E E and C. Let

(Equation Omitted)

where

(Equation Omitted)

Northwestern University Page 1 Dec 31, 1979

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MAPPING CONSIDERATIONS IN THE DESIG~ OF SCHEMAS FOR THE RELATIONAL MODEL

relation in E k and

(Equation Omitted)

is a relation in C. Several mapping are of interest:

1. relations mappingeee That is,,al constructs the

relation e k E E from the rela tions C' in

(Equation Omitted)

. tuples mapping: a

(Equation Omitted)

where

(Equation Omitted)

is a tuple in e i . The

fu nction 01 maps a tuple of e k to a tuple or a set of tuples in

(Equation Omitted)

3. operations mapping:

(Equation Omitted)

where y maps the set of operators on

(Equation Omitted)

in V to a set of operators on the tuples of C' defined

(Equation Omitted)

Alternatively, y.,can be defined in terms of operations on relations instead of tuples (e.g. join).

The normalization process in the relational model [14,15,16] has been developed to avoid certain types of update anomalies in the relations. This normalization is usually performed without regard to its effect on the mapping...