UML is more natural than ER

UML talks on different abstraction layers

Opponent: UML allows integrated consideration of application specification at various abstraction levels.

Proponent: This property is one of the very strong properties of UML. In practice database specifications are large and are used for the display of different views on the same application. Thus, we have to integrate zooming, modularization and abstraction into modeling. The abstraction layer model enables in abstraction in any granularity. UML has only a two-step abstraction. HERM has an abstraction on various layers and allows to cope with various design phases at the same time.

Opponent: But two step-abstraction is powerful enough. Use cases can be directly refined to class diagrams and all the other diagrams.

Proponent: Sorry again, whenever we want to survey a large and complex application use case diagrams become very large. Further we cannot concentrate on one aspect of the application not considering all the others.

Opponent: But this has been done with packages!

Proponent: Packages of use cases?

Opponent: No, packages of classes.

Proponent: Then we cannot use abstraction for use cases.