text: Suppose we want to create a class called VegetarianPizza. Individuals that are members of this class 
  can only have toppings that are a CheeseTopping or VegetableTopping. To do this we can use a 
  universal restriction: 
  
  **Exercise 22: Create a Defined Class called VegetarianPizza**
  
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  1. Select the Pizza in the Classes tab. Create a subclass of Pizza and name it VegetarianPizza. 
  
  2. Make sure VegetarianPizza is selected. Click on the Add icon (+) next to the SubClass Of field in the 
  Description view. 
  
  3. Select the Class expression editor tab from the pop-up window. Type in the Description Logic axiom: 
  hasTopping only (VegetableTopping or CheeseTopping). Click on OK. 
  
  4. Make sure VegetarianPizza is still selected. Run the Edit>Convert to defined class command. 
  
  5. VegetarianPizza should now have three horizontal lines through it just as CheesyPizza does. 
  Also, the Equivalent To field in the Description view should have: Pizza and (hasTopping only 
  (CheeseTopping or VegetableTopping)). Note that another way to create defined classes is to enter the 
  Description Logic axiom directly into the Equivalent To field. 
  
  6. Synchronize the reasoner. 