* Most operators perform <<.def relative>> to their input. They examine each input title in turn and filter out any that don't match. Such steps narrow down the output of a run.
* <<.def Absolute>> operators ignore their input and generate an independent output instead.
A good example of an absolute operator is <<.olink title>>. The output of `[title[A]title[B]]` is just <<.tid B>>. But the <<.olink field>> operator is relative, so `[title[A]field:title[B]` outputs nothing at all.
