Schema Translation - Information Systems Reengineering, Integration and Normalization - page 131

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Fig. 3.60 Map categorization into a complex element choice in XSD

could recover the lost semantics by mapping logical network schema or hierarchical
schema to the EER model. Such process is called reverse engineering. We can then
map the EER model to another logical schema such as relational schema in for-
ward engineering. Similarly, we can map relational schema into an object-oriented
or XML schema. The knowledge engineering approach is to abstract primitive se-
mantics such as parent-child relationships in the data structure of the hierarchical
or network database from the DDL, and confirm the advanced semantics such as
generalization, categorization, and aggregation from the users.
Similarly, we can map relational schema to the EER model in reverse engineer-
ing with user's assistance to recover the lost semantics. The process is to make
use of the various keys in the existing relation, for example, primary keys, foreign
keys, composite keys, and the components of the composite keys. These keys, along
with the IDs, the constraints of the relations, can be used to reconstruct primitive
semantics of the schema. For the advanced semantics, user's inputs are also needed.
Once the EER model is reconstructed, we can then map the EER model to the UML
model, a conceptual model for an object-oriented database, in forward engineering.
We can map the UML model to an object-oriented database schema. Similarly, we
can map an EER model into a DTD Graph or XSD Graph.
The translation from an XML view of relational schema into an XML schema
can be accomplished by recovering data semantics from relational schema into its
conceptual schema in EER model. Once these constraints are defined, we can se-
lect relations that can represent the XML view from the relational schema. The