The type xs:long represents an integer between −9223372036854775808 and 9223372036854775807 inclusive. It is ultimately derived from xs:decimal, via xs:integer. Its value can be a sequence of digits, optionally preceded by a sign (+ or −). For example, −9223372036854775808, 0, 1, and +214 are valid values. Because implementations are only required to support integers up to 18 digits, some may not accept the full value range of xs:long.