title: UML Papyrus association notation
body: <p>I am creating an UML class diagram on Papyrus but I can't understand the notation used for associations. 
  When an association is set to be navigable, the tool adds a black dot on the tip of the arrow as default notation. I was able to remove the dot by changing the member end owner from <em>classifier</em> to <em>association</em>. 
  What is the conceptual difference between the two? I can't find any discussion on the concept of classifier in my UML book...</p>
  
  <p>Thank you!!</p>
  
  <p>PS: I'm using papyrus 4 on Eclipse Juno</p>