title: How to merge decision/fork nodes in UML
body: <p>I have the below UML activity diagram for a shopping cart use case. It has several decision and fork nodes but there are no corresponding join/merge nodes. Could you please show me:</p>
  
  <ul>
  <li>how to correct the diagram by introducing the merge/join nodes.  </li>
  <li>how to modify the diagram so that a customer can repeat the process (of adding more products to the shopping cart).</li>
  </ul>
  
  <p>Thank you.
  <img src="https://i.stack.imgur.com/z3GsA.png" alt="enter image description here"></p>