Oracles SQL Developer 2.1...

On december 15th Oracle released a new version of its database tool SQL Developer:

Version 2.1.0.63.73

They jumped from version 1.5.5 to 2.1.0, so there should be some really new features built in. The release notes tell us:

Oracle SQL Developer Unit Testing provides a unit testing framework that allows you to build a set of sequential steps to create test cases for testing your PL/SQL code. These tests can optionally be collected into test suites, which can then be run and rerun to verify required functionality after any changes to your PL/SQL code. Command
line access for executing, exporting, and importing suites or tests is provided for integration with your build and version control environment.

SQL Developer 2.1 incorporates a Data Modeler viewer, integrated into SQL Developer. The Data Modeler Viewer also supports visualizing tables, views and object types on read-only Data Modeler diagrams. The SQL Developer Data Modeler Viewer extension is a free extension to SQL Developer. For a updateable data model, download and review the Oracle SQL Developer Data Modeler, a stand alone product that supports logical,
relational and conceptual modeling. The tool supports forward and reverse engineering and import and export from various sources. The Data Modeler supports an additional standalone model viewer, which allows users to open models built in the full Data Modeler.

The SQL Worksheet has been redesigned for SQL Developer 2.1 to support concurrent task processing for long running operations. Updates to the worksheet include the support of multiple data grids off the F9 (Run Statement) command and dockable OWA, DBMSOutput and SQL  History windows.

A detailed explanation is given here.

Let's focus on the second point: Data Modeler

I tried to work with that tool, but without the documentation or tutorial you are really lost. The official documentation does not explain anything useful about the data modeler...
After searching a while i found some some nice links to start:

• Create a data model from the database
• Start with a DDL-File
• Drag and Drop ERD
  

After at least the first tutorial you will be able to maintain your ERD with SQL Developer 2.1...