title: Use case diagram -usage of "includes"
body: <p>consider the follwing use case diagram<br>(say the user login to a system, fills a form and submits to the server)</p>
  
  <pre><code>   (Fill in Form) --&lt;&lt;includes&gt;&gt;----&gt;(Login)
              ^
              \                         ^
            &lt;&lt;includes&gt;&gt;               /
                \                     / 
              (sumbit)------&lt;&lt;includes&gt;&gt;     &lt;------- Is this include necassary ?
  </code></pre>
  
  <p><br>  <code>now "Submit" includes "Login"</code><br>
   <code>again "Submit" includes "Fill in Form" which includes "Login"</code></p>
  
  <p>The two 'includes' seem unnecassary.<br>By including "Fill in Form" it automatically includes "Login" or not? What is correct? <br></p>