Data Conversion - Information Systems Reengineering, Integration and Normalization - page 142

In order to separate the restructuring process from the source and target conver-
sion function of the translator, normal form of data is introduced. A data structure
expressed in the normal form will be viewed as a set of N-tuples of the form.

Re f-Name < Item, Item ……>

The normal form presented here has two types of N-tuples: a data structure instance
N-tuple and a relationship N-tuple.
The data structure instance N-tuple consists of the following: Data Structure
Instance Name (Ref-Name), Identifier (unique), and Data Item(s).
The relationship N-tuple consists of: Relationship Name (Ref-Name) and identi-
fiers of all data instances involved in the relationship.
For instance, the following Cobol structure:

Level 0 PERSON

1 NAME GE CARS

2 LIC# 1 MAKE ACCIDENT

3 LIC# 2 NAME

Can be expressed in using these SDDL statements:

Data Structure PERSON <NAME, AGE>

Instance CARS <LIC# 1 , MAKE>

N-tuples ACCIDENTS <LIC# 2 , NAME>

Relationship PERSON-CAR <NAME, LIC# 1 >

N-tuples CAR-ACCIDENT <LIC# 1 , LIC# 2 >

To translate the above three levels to the following two levels data structure:

Level 0 PERSON

1 NAME GE CARS

2 LIC# 1 MAKE

LIC# 2 NAME