oriak is a minor PITA to install... but very minor...
It gives a riak storage back-end for ORDF. To install it you must first install the Google protobuf python bindings. On your system it may come packaged. On mine it didn't. Because of the way it builts you cannot use pip or easy_install to install it. Installing protobuf is easy but beyond the scope of this document.
Once you have installed protobuf it should be fairly smooth sailing. Just install oriak in the normal way, with pip or easy_install and it should install the riak python bindings and register a handler plugin for ORDF.
How is this used then? Graphs saved will be saved in a structure that looks like this:
- "name": "http://uri_of_graph", "content": "... RDF/XML serialised graph"
When reading or saving a graph it will do so non-destructively so that any additional fields in the document that are used in other ways by other applications (e.g. map/reducs) will be preserved.
The name of the document is the SHA256 hash of the graph URI.