In this strategy, each class is mapped to a separate table. When transforming an OOM to a PDM, PowerDesigner only generates tables for leaf classes, and assumes that all other classes are not mapped to a table, even if you manually define additional mappings. The MappedSuperclass annotations are generated for those classes, and the Inheritance annotation will not be generated for all the classes. You need to customize the generated annotations and create additional tables if you want to map classes other than leaf classes to tables.
@MappedSuperclass
public class Shape { .. }
@Entity(name="Rectangle")
@Table(name="Rectangle")
public class Rectangle extends Shape { ... }