Stop using Circle/Square/Rectangle, People/Employee, Car/Model examples for models or example on how to use Object-Oriented Principles or any example at all.
There is plenty of "Open" model that you can use. Here's a simple list for those who needs inspiration:
- Blog (Posts, Comments, Authors, etc...)
- E-Commerce (Invoice, Order, Customer, Warehouse, Inventory, etc...)
- Auction (Auction, Seller, Buyer, Reputation, etc....)
- Bank (Account, Transactions, Customer, etc...)
- News site (Article, User, Approver, etc...)
- And so many more
Unless you are explaining what is OOP to total beginner that never did any of this, you should use more advanced model to explain practices, design patterns or anything else. Otherwise, we'll keep on babbling on stupid model how a Square is a Rectangle and so on.
The time has come to stop using 1st grade model to explain advanced concept. Most people should be able to easily pick one of the model I've shown above and display one element of the model to easily make it available to everyone.
Who's with me?