title: UML sequence diagram, call
body: <p>Let's say we have three classes <code>A, B</code> and <code>C</code>, and an instance <code>a</code> (resp. <code>b</code>/<code>c</code>) of type <code>A</code> (resp. <code>B</code>/<code>C</code>).
  Suppose that <code>b</code> is an attribute of <code>a</code> and <code>c</code> is an attribute of <code>b</code>.</p>
  
  <p>In a method of <code>a</code>, the following is called : <code>b.c.operation()</code> </p>
  
  <p>How can we represent this  in a sequence diagram ?</p>