the usage of ccc:fid is an extension of the namespace which needs to be declared in xml in order to be able to use it in libraries like simplexml.
Here are some examples of descriptions of usin a namespace:
- http://www.w3.org/TR/1999/REC-xml-names-19990114/
- http://www.w3.org/TR/xml-names/
Hope that helps, albeit it is a little complicated.
