Database Reference
In-Depth Information
1. Semantic Modeling Approach
(
used for large, complex databases
):
• Create Semantic Data Model
• Transform Semantic Model to Relational Model
Real-world
Information
Semantic
Data Model
Relational
Data Model
2. Traditional Approach
(
used for smaller, simpler databases
):
• Create random two-dimensional table structures
• Normalize the data structures
Normalized
Relational
Data Model
Real-world
Information
Random
Tables
Figure 8-19
Relational data model: design approaches.
entity-relationship data modeling technique. Either of these techniques will produce
a semantic data model that can be used to create the relational data model.
Here are the steps in this design approach:
•
Gather the information requirements of the organization.
•
Create semantic data model to truly represent the information requirements.
•
Review the overall semantic data model for completeness.
•
Take each component of the semantic data model at a time and examine it.
•
Transform each component of the semantic data model into a corresponding
component of the relational data model.
•
Pull together all the components of the relational data model resulting from
the transformation from the semantic data model.
•
Complete the relational data model.
•
Review the relational data model for completeness.
Chapter 9 elaborates on this approach to designing the relational data model. We
will list the components of the semantic model and the corresponding components
of the relational model. We will determine how each component of the semantic
data model must be mapped to its corresponding component in the relational data
model.
Traditional Method
Before the introduction and standardization of data modeling techniques, database
practitioners had traditionally adopted a different method. A relational data model
is, after all, a set of two-dimensional tables. Why not look at the information require-
ments and try to come up with the necessary tables to represent the data that would
satisfy the information requirements? Why do you need an intermediary step of
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