provides attributes for defining a mathematical formula. A formula is provided to describe a mathematical calculation such as a conversion between measurement systems. The stadium was a Roman unit of linear measurement equivalent to 625 pedes, or Roman feet. In the Potrzebie system of measures as introduced by Donald Knuth, the whatmeworry unit of power is equivalent to one hah per kovac. The kilowhatmeworry is equivalent to 1000 whatmeworries. One unit of aeolipower (A.P.) is equivalent to 100 kilowhatmeworries.

This attribute class provides formula for use in defining a value used in mathematical calculation. It can be used to store a mathematical operation needed to convert from one system of measurement to another. We use the teidata.xpath datatype to express this value in order to communicate mathematical operations on an XML node or nodes. The $fromUnit variable notation simplifies referencing of the fromUnit attribute on the parent conversion element. Note that div is required to express the division operator in XPath.