The details of this step depend upon the database management system or file access method adopted. There are three main approaches adopted by those who implement the database management system:
- No perceived record concept exists -
For example: VSAM files
If this approach is applicable, this subtask is omitted.
- Only perceived records may be referenced by programs -
For example: TIS/LUV
In this approach, a set of ideal perceived records is designed for each procedure within the implementation area. It may be practical to allow each procedure to have its own set of perceived records, which will enhance program and data independence considerably.
If it is impractical to support so many sets of perceived records, the perceived records are aggregated into a unified collection that will support all processing requirements of the implementation area. Do this by identifying duplicated record types and by merging record types having the same key. The database designer has to define to the database management system how the perceived records are to be built from the underlying records (i.e., those defined in the refined data structure).
- Programs may reference perceived and underlying records -
For example: ORACLE, DB2
In the third approach, perceived records are defined only when it is useful for program development, maintenance, or security, or for end-user query languages and analysis packages. The database designer needs to define to the database management system how the perceived records are to be constructed from the underlying records.
» Creates deliverable D4.22.1 Program Specification.
» Creates deliverable D4.7.8 Perceived Data Structure Diagram.
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Activity Overview : A4.10
Stage Overview : Design Stage
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