Over the years, Energistics has accumulated several specifications related to units of measure. The Epicentre Data Model contains standard instance data for unit symbols and for unit conversions (based on the SPE’s The SI Metric System of Units and SPE METRIC STANDARD, 1984). The Epicentre information was the source for the Unit of Measure Dictionary (currently v2.2) that is used by most current Energistics XML specifications (e.g., WITSML).
Energistics also is responsible for the Recommended Practices for Exploration and Production Data Digital Interchange (RP66 v2) specification which contains a unit model.The RP66 unit model defines an algorithm for creating a unit symbol as opposed to the explicit list of unit symbols defined by Epicentre.
Finally, Energistics developed a Quantity Class specification that assigns unit symbols to a high level quantity term. These classes are utilized, for example, by WITSML to define data types which constrain the allowed unit symbols for a quantity.
DRAFT ENERGISTICS UNIT OF MEASURE SPECIFICATION - UNDER DEVELOPMENT
Currently, Energistics is attempting to unify all of the above specifications into one coherent package. It will be primarily based in the Unit of Measure Dictionary and Quantity Class specifications but the symbols will conform to the RP66 algorithm. The information requirements of PPDM and the SEG will be an additional consideration in the final results. Yet another consideration is to update the conversion information to account for the increased accuracy available in modern 64 bit computers. The International System of Units, universally abbreviated SI (from the French Le Système International d’Unités), will represent the underlying basis for all of the results. The
initial draft only addresses the SI subset but other units will be addressed in later drafts.
INTEGER CODES
Associated with the above draft unit specification, a set of
integer codes has been defined for use in special cases where only a binary value can be used. The Society of Exploration Geophysicistsis using these codes as part of their new “SEGD Rev3.0” format. The semantics of these codes will not change as the above specification is finalized.