nonPositiveInteger data type
The xs:nonPositiveInteger data type represents an integer that is less than or equal to zero. Derived from the xs:integer data type.
The lexical form of xs:nonPositiveInteger is an optional
preceding sign that is followed by a finite-length sequence of decimal
digits. For lexical forms that denote zero, the sign can be negative
(-) or can be omitted; in all other lexical forms, the negative sign
(-) must be present. The range that can be represented by this data
type is from -9223372036854775808 to 0. The following numbers are
valid examples of this data type: -1, 0, -12678967543233,
and -100000.