[2] 非負整数 (non-negative integer) は、 非負の整数です。

[1] Packaged Web Apps (Widgets) - Packaging and XML Configuration (Second Edition) ( (2012-11-22 21:22:20 +09:00 版)) <http://w3c.github.com/packed-webapps/packaging/#rule-for-parsing-a-non-negative-integer>