title: How can I reference content in Alfresco and ensure that the reference is 100% unique
body: <p>I am working with the Alfresco web service and looking at using it with another web application for content management. Our other web application will need a way to reference content that exist in Alfresco. </p>
  
  <p>Are the Reference uuid's that alfresco generates guaranteed to be unique and are they guaranteed to even exist? I read in a wiki page that the uuid may be optional. I take that to mean that they may not even always exist and I guess could be null. The more I read the  If it does not always exist or can be null is there a better identifier for content inside Alfresco? This is to be used with medical data so I need a 100% unique way to reference content that is stored in alfresco.</p>
  
  <p>Link where I read that the UUID was optional:
  <a href="http://wiki.alfresco.com/wiki/Web_Service_Data_Types" rel="nofollow">http://wiki.alfresco.com/wiki/Web_Service_Data_Types</a></p>