ACTION-2016-02-25-003 - bug 29455 - on-empty

ACTION-2016-02-25-003: MK to rack his head and/or thesaurus to find an
alternative to 'significant' and 'insignificant' for the discussion of
xsl:on-empty and bug 29455.

I propose "vacuous".

Here's a flavour of how it reads:

[Definition: an item is *vacuous* if it is one of the following: a zero-length text node; a document node with no children; an atomic value which, on casting to xs:string, produces a zero-length string; or an array which on flattening (using the array:flatten function) produces either an empty sequence or a sequence consisting entirely of vacuous items.]

An xsl:on-empty instruction is triggered only if every preceding sibling instruction, text node, and literal result element in the same sequence constructor returns either an empty sequence, or a sequence consisting entirely of *vacuous* items.
...
An xsl:on-non-empty instruction is evaluated only if there is at least one sibling node in the same sequence constructor, excluding xsl:on-empty and xsl:on-non-empty instructions, whose evaluation yields a sequence containing an item that is not *vacuous*. If this condition applies, then all xsl:on-non-empty instructions in the containing sequence constructor are evaluated, and their results are included in the result of the containing sequence constructor in their proper positions.

Michael Kay
Saxonica