title: primary/foreign keys in uml
body: <p>I am doing a UML model based on my ERD generated with <a href="http://www.mysql.com/products/workbench/" rel="noreferrer">MySQL workbench</a>. But now i have a doubt about the primary and foreign keys representation in a class diagram.</p>
  
  <p>In the traditional UML diagram we should include the primary keys as atributes of each class? For example, the <code>id_user</code> or the <code>id_list</code> ? And about the foreign keys ? These ones are ignored as attribute but reflected as associations? </p>
  
  <p>thanks</p>