The short description and searching

["Guy K. Haas" <guy@hiskeyboard.com>]

In this sentence from the DITA 1.2 description of shortdesc

     The short description, which represents the purpose or theme of the
topic, is also intended to be used as a link preview and for
searching.

what does "for searching" mean?

I know that a <shortdesc> text is supposed to be the blurb that appears in
a search engine's results.  But the only way I can conceive of <shortdes>c
to "be used ... for searching" is that, when the topic is published as
HTML, the <shortdesc> text is output in the HTML <abstract> element
(unless a larger <abstract> is in the topic's metadata, in which case THAT
is used).

Is that what the "for searching" means?  What about other file types, such
as PDF?

--Thanks,
      Guy