VBM - Vision Based Methodology™

Activity 7: Creating the Vision

Race to the Database

Now is the time to begin transforming the Entity/ Relationship Diagram into a Physical Database Design. During the upcoming prototyping process the transformed data architecture should be used as a source for the screen (window) and report fields. At the end of the Business Design phase, a perfect match should exist between the finalized layouts and the completed database design.

The following transitional process can be undertaken to convert the logical data model to a physical data model:

1. Examine the unique characteristics of the data management architecture that will be the ultimate "target" of the database design.
2. Examine the attributive entities (the "repeating" information). If the number of anticipated occurrences is very low, these attributes may be moved to the parent entity and repeated for the number of expected occurrences (denormalization). If additional occurrences may be required in the future, it is better to leave the attributive entity as is (normalized).
3. Some IS Departments require that all "type" entities be put into one "code table" entity with a high order Table ID attribute. Depending on the target database architecture this may or may not be an acceptable practice. In general, leaving these entities broken out will more clearly help in identifying potential data joins and unions.
4. The subtype attributes should be examined both for the number of occurrences and the number of attributes. If both are very low, combining the attributes into the parent entity may be acceptable. Again, the same judgement should be used as above.
5. All "processing" flags, switches, and indicators can begin to be included in this model.
6. Volumetric information should be taken into account in order to predict table and file sizes.