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A forward contract is a private and customizable agreement that settles at the end of the agreement and is traded over-the-counter. A futures contract has standardized terms and is traded on an exchange, where prices are settled on a daily basis until the end of the contract.
During the call today we made changes to incorporate the above, and eliminated the redundant and somewhat confusing notion of a non-physical underlier, which included commodities (it could have included commodity contracts, but ... it was not widely used and it made more sense to eliminate it altogether). Elisa will post the resulting work to a pull request using WIP in the title, since we have more to do on this ontology to make it releaseable.
A couple of additional notes:
(1) an example ontology that includes units of measure that are relevant for commodities, such as agricultural and geological units, is https://bioportal.bioontology.org/ontologies/OM. It includes troy ounces, US barrels, bushels, and other relevant units. Perhaps we can come up with an example contract that uses this as the basis for the units referenced.
(2) a list of relevant commodities referenced in foreign trade is provided by the Census Bureau at https://www.census.gov/foreign-trade/schedules/b/2014/index.html, including abbreviations for various quantities and conversion tables for measures and weights. My favorite abbreviation: "n.e.s.o.i", which stands for "Not elsewhere specified or included".