Going through the Open PHACTS (https://www.openphacts.org/) website I just found some more great resources for this project:
- Encoding Units and Unit Types in RDF (http://www.openphacts.org/specs/units/)
- Guidelines for Exposing Data as RDF (http://www.openphacts.org/specs/rdfguide/)
- QUDT - Quantities, Units, Dimensions and Data Types Ontologies (http://www.qudt.org/)
- Ontology of Units of Measurement (https://code.google.com/p/unit-ontology/)
If only the guys developing SWEET (http://sweet.jpl.nasa.gov/ontology/) and those developing QUDT at NASA could join forces with NIST and UnitsML (http://unitsml.nist.gov/) then we could have something definitive...