An integer shorthand identification for an expression.
An ExpressionIndex corresponds one-to-one to an
ExpressionName.
Once assigned an ExpressionIndex may not be changed.
ExpressionIndexOrZero
uint32
Either an ExpressionIndex or zero. The meaning of zero
depends on the DESCRIPTION of the object.
ExpressionName
binary
This data type is a refinement of DisplayString to
represent an identification for an expression. An
ExpressionName corresponds one-to-one to an
ExpressionIndex.
This identification of an expression is subject to change
only by administrative request.