O/R Mapping Modeling

PowerDesigner not only supports object-oriented modeling and data modeling, but also supports O/R Mapping modeling between OOM and PDM objects.

The following table lists object mappings in these two model types:

OOM Element	PDM Element
Domain	Domain
Class (only if the Persistent and Generate checkboxes are selected in the class property sheet)	Table
Attribute Column (only if the Persistent checkbox is selected in the attribute property sheet)	Column
Identifier	Identifier
Association	Reference or table
Association class	Table with two associations between the end points of the association class
Generalization	Reference

You can define mappings between these two model types in any of the following ways:

Top-down approach – define classes, generate database schema and O/R mapping
Bottom-up approach – reverse engineer a database or define new database schema, generate classes and O/R mapping
Meet-in-the-middle – manually define O/R mapping using the visual mapping editor

Applying Top-Down Approach
In order to apply well-defined O/R Mapping strategies, PowerDesigner provides default transformation rules for model generation. We will introduce these rules in detail in the following sections. You can also customize transformation using persistence settings and generation options.
Applying Bottom-Up Approach
Bottom-up approach is much more like top-down approach, except that transformation happens in reverse direction.
Meet in the Middle
If you have existing OOM and PDM, you can also define mapping between them manually. The O/R Mapping models in PowerDesigner are platform independent.