How can I reference content in Alfresco and ensure that the reference is 100% unique

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.

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.

Link where I read that the UUID was optional: http://wiki.alfresco.com/wiki/Web_Service_Data开发者_如何转开发_Types

A UUID is always unique. What you have read at the web services data is about providing an optional UUID.

How content is stored in Alfresco is like this.

A UUID points to a set of content (Wrapper), this set contains the actual object and metadata. You see the linking quite good when using versioning. You'll see that the same UUID points to even the updated content + metadata.

So it's guaranteed that it remains unique. Of course, if the content will be deleted so will the UUID.

I'd rather use the new CMIS implementation CMIS Link, than the webservices. Not that they aren't sufficient, but they are quite outdated and sometimes you need multiple WS call, which can be done in one CMIS call.