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lenge. You have to make sure that all modelers adopt the same set of
modeling conventions. It is a good practice to integrate all the partial semantic
models first and then transform the whole semantic data model into a relational
data model.
Verification with requirements.
At each step, you need to check back with the infor-
mation requirements and verify that the evolving semantic model is a true repre-
sentation. This verification becomes especially important when the database system
tends to be large.
Review for completeness.
Do not neglect to make sure that all portions of the
information requirements are reflected correctly and completely in the final rela-
tional data model.
MAPPING OF COMPONENTS
While creating an object-based data model, the data modeler uses the components
or building blocks available in that technique to put together the data model. You
studied these components in sufficient detail in Chapter 6. Similarly, to create a rela-
tional model, the building blocks are the ones available in the relational modeling
technique. You reviewed these components in Chapter 8. Essentially, transforming
an object-based data model involves finding matching components in the relational
data model and transferring the representation of information requirements from
one model to the other. Model transformation primarily consists of mapping of
corresponding components from one data model to the other.
Let us recapitulate the components or building blocks for each of the two
models—the semantic and the relational data models. The list of components makes
it easier to begin the study of component mapping and model transformation.
Semantic data models
Object-based data model
Object sets
Attributes
Identifiers
Relationships
Cardinalities
Supersets/Subsets
Entity-relationship data model
Entity Types
Attributes
Keys
Relationships
Cardinality Indicators
Generalization/Specialization
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