The specification is a little ambiguous as to whether xsl:use-package is allowed as a child of xsl:stylesheet/xsl:transform (rather than only allowing it as a child of xsl:package). The WG discussed the matter and we decided that we intended to allow it.

The changes needed to clarify this appear to be:

(a) allow it in the schema for stylesheets

(b) in the element syntax summary (appendix D), list xsl:stylesheet and xsl:transform among the permitted parents of xsl:use-package

(c) in 3.7, add xsl:use-package to the list of declarations allowed as a child of xsl:stylesheet

(d) in 3.5, in the description of the "package manifest", there are only two kinds of element it can contain: xsl:expose, and declarations that can also appear in xsl:stylesheet. xsl:use-package and xsl:global-context-item should no longer be treated as if they are different.