Working Memory
   - Types of WM items
 
   - Just like structured programming, items can have types  
 
   - You can enumerate values  
 
   - or have integer, real or really anything.
 
   - In Clips you can also have complex templates and objects.
 
   - Subclasses are specialisations of Classes.
 
   - A mammal class, might have a specialisation of primates.
 
   - The classes have slots.
 
   - This is essentially a frame.
 
   - Rules inspect working memory and can change it.