Definitions for "Literal value"
Keywords:  integer, unquoted, ncl, scalar, float
In an expression, a series of characters that literally signifies a value of type integer, float, truth-value, text, or symbol.
NCL: A single scalar value expressed by its actual string value (i.e. not referenced by a variable). For example, 1, 1.414 and "string" are literal values.
a default for when the attribute is not given a value