Redland I believe associates every statement with a "context" so the context can provide any provenance info. These sort of things are fine internal within a system but aren't too helpful if you want to share that info and/or use it as part of the RDF (RDFS/OWL) inferencing.
Long-term (i.e. it's unlikely to be in a W3C spec in the near future) there's Named Graphs as a very promising extension of RDF, for which the theory has been worked out and is nice & intuitive.
A third approach to provenance is already supported by RDF,
reification. I still get very confused over this, Shelley Powers
called it "The Big Ugly". It's a bit like quotation but /different/ -
there is explanation in the Primer [2]. I've not used it myself, but a
presentation I saw last week convinced me the approach can work
cheers Bill