This is a synonym of <xsl:stylesheet> , described on page 433. The two element names may be used interchangeably.
Why is it useful to have two names for the same thing? Probably because it's the easiest way for a standards committee to keep all its members happy. More seriously, the existence of these two names is indicative of the fact that some people see XSLT as being primarily a language for transforming trees, while others see its main role as defining presentation styles. Take your pick.
<xsl:transform id? = id extension-element-prefixes? = tokens exclude-result-prefixes? = tokens version = number xpath-default-namespace? = uri default-validation? = "strict" "lax" "preserve" "strip"> <!-- Content: (xsl:import*, other-declarations) --> </xsl:transform>
<xsl:stylesheet> on page 433