Oracle Modeler Overview
http://www.oracle.com/technetwork/developer-tools/datamodeler/overview/index.html
- you can find out more about the modeler
Site for downloading
http://www.oracle.com/technetwork/developer-tools/datamodeler/downloads/index.html
SQL Developer Data Modeler User's Guide
http://docs.oracle.com/cd/E48219_01/doc.40/e48205/toc.htm