expr 

Note: this expression is has been useful to include when the type is, e.g. linoid, to remind users of the form of the equation.
However, it's use should be discouraged, as it could be assumed that changing this attribute can change the form of the equation (as for generic_equation_hh).
It's better to include the form of the equation as a comment, as in the examples. This attribute may be removed in v2.0

Attribute Information

Used By

Complex Type Deprecated_AkdEquation

Source 

<xs:attribute name="expr" type="xs:string">
  <xs:annotation>
    <xs:documentation>Note: this expression is has been useful to include when the type is, e.g. linoid, to remind users of the form of the equation. However, it's use should be discouraged, as it could be assumed that changing this attribute can change the form of the equation (as for generic_equation_hh). It's better to include the form of the equation as a comment, as in the examples. This attribute may be removed in v2.0</xs:documentation>
  </xs:annotation>
</xs:attribute>

Sample