[Pharo-project] Customizing Explore

[Ben Coman]

I want to customize the Explorer that comes up when you press 
<shift><alt><i> such that as well as browsing my model, I can have a 
custom menu on each displayed class to instantiate one of the 
relationships defined on that class.  For example, if the Explorer shows 
a Library object, then right-clicking on that object will bring up a 
menu with item "Add book".

What are the classes I should be looking at for examples?
cheers, Ben