 .]
</span>
Keywords are any word, or set of words, that identify a database
record unambiguously.  Thus, if you have only one database record for
the author Ray Bradbury, 
<br/>
<span class="pre-in-pp">
  .[
  bradbury
  .]
</span>
is sufficient.  However, if your database contains several records
for books by Bradbury, say, <i>Fahrenheit 451</i> and <i>The
Martian Chronicles</i>,
&#8220;<kbd>bradbury&nbsp;451</kbd>&#8221; and
&#8220;<kbd>bradbury&nbsp;martian</kbd>&#8221; would identify the two records un