Object Relationship Notation (ORN) is a declarative scheme for defining common relationship, or association, semantics. The ORN Simulator is a tool that allows one to become adept at relationship design and data modeling using ORN. In the ORN Simulator you can graphically define relationships and then observe and fine-tune their semantics as you create and delete objects and create, destroy, and change relationship instances in a prototype, or toy, database. You view the database in the context of an Entity-Relationship Diagram or a UML class diagram. Once the desired relationship behavior has been defined and verified in the toy database, you can implement this behavior in a real database using a Database Management System (DBMS). If this DBMS supports ORN, the implementation will require no programming and no specification of complex constraints and triggers.

The ORN Simulator is an excellent tool for teaching the concepts of data modeling and database transactions.

To run the ORN Simulator at any time, simply click on Run ORN Simulator. (Note: The ORN Simulator requires the Java Plug-in when using Internet Explorer.)

The ORN Simulator is implemented with a front-end user interface component and a back-end database management component. The front-end is implemented in Java and runs as an applet client. The back-end is currently implemented in Java and C++ and runs as a server. Communication between client and server is via Java's Remote Method Interface (RMI). Currently, the remote methods are Java native methods coded in C++, which call C++ methods defined on an object database. C++ code manipulates the database using Object Relater Plus (OR+), an ODBMS prototype, which implements ORN as an extension to ObjectStore from Progress Software.