This ontology defines a set of properties which may be used for reprenting physical quantities. Each is an RDF Property which realtes a quantity to a number which expreses the quantity in that expressed that quntity in the given unit. :bed ex:length _:a. _a: m 2. Property chaining is the equivalent of unit multiplication. Inverse properties correspond to reciprocal units. Because conventional signs for units are very case-sensitive, this ontology breaks from the normal convention that all property localnames begin with lowercase. See also http://www-ksl.stanford.edu/knowledge-sharing/papers/engmath.html