1. A data structure tangibly embodied on a computer readable storage medium, the data structure comprising: a plurality of measurement statement objects S representing a plurality of measurements M, wherein each of the plurality of measurement statement objects S n corresponds to a particular one of the plurality of measurements M n and comprises: a value object representing a value; an aspect object representing an aspect of the measurement M n , wherein the value is a value of the aspect of the measurement M n ; and an entity object representing a physical entity measured by the measurement M n , wherein the aspect of the measurement M n is a measurable aspect of the physical entity measured by the measurement M n .