self.eContainer().interfaces.add(p);

context mylibrary!Library{
	
	critique InstantiateModelElement {
		
		check  :  mylibrary!Library == null 
		 	 		
		message : "Instantiate model element"  
		
		fix {
			title : "Create a new book"
			
			do {
				mylibrary!Book.createInstance;
				  //self.eContainer().Book.add(new mylibrary!Library); Im trying this way, but doesn't working		
			}	
		}
	}
	
}

do {
  var book : new mylibrary!Book;
  // Note that if you're only running the constraint
  // against one model, var book : new Book would 
  // work equally well (i.e. you don't need "mylibrary!")
  self.books.add(book);
}