title: How to show attribute as "readonly" in UML?
body: <p>I want to describe some models of an API in a diagram. Is there a standard how to mark an attribute as <code>readonly</code>? These attributes are set by the system and cannot be modified by the API consumer.</p>
  
  <p>Currently I abuse the class diagram notation for <code>private</code> and <code>public</code> attributes. But I am not satisfied with this.</p>
  
  <p>Thanks for your thoughts :)</p>