The expression some $x in E1 satisfies E2 returns true if there is an item in the
sequence E1 for which the effective boolean value of E2 is true.
Note that E2 must use the range variable $x to refer to the item being
tested; it does not become the context item. For example, some $x in @* satisfies $x eq ""
is true if the context item is an element that has at least one zero-length attribute value.
Similarly, the expression every $x in E1 satisfies E2 returns true if every item in the
sequence given by E1 satisfies the condition.
