Generating the database schema

General principle

Generation for relational databases takes into account the model in terms of its:

· classes

· associations

· generalizations

· attributes

Using tagged values

Tagged values describe specific RDBMS notions in the Objecteering model. The characteristics of the target RDBMS (cluster, structure, etc.) can be accessed using additional tagged values.

Furthermore, parameterization lets you add your own tagged values, in order to adapt SQL Designer to your own specific generation operations.

Mapping rules

The rules for mapping object model notions in the tables of a relational database are as follows:

The ... object model	relational databases ...
class	table
association	table or columns and outside keys
instance	not managed by Objecteering SQL Designer
attribute	a table's column
generalization	3 alternatives: one table per concrete class (with copying specialized attributes) , one table per class( without copying specialized attributes), or only one table for the complete hierarchy
{primaryKey} tagged value	primary key
{index} tagged value	index
one or more packages	according to the stereotype (schema, database, physical model)

Example

Figure 17. Example of mapping

This gives the following in SQL:

CREATE DEPARTMENT TABLE(

NUMBER...,

NAME...,

LOCATION...);