r</i></td><td valign="baseline">&nbsp;&nbsp;&nbsp;&nbsp;</td><td valign="baseline"> An <a href="ref-glossary.html#id64">extended&nbsp;event-class&nbsp;specification</a> 
(see below; default is <code>t</code>)
</td></tr><tr valign="top"><td valign="baseline" nowrap><i>unit-class-or-instance-specifier</i></td><td valign="baseline">&nbsp;&nbsp;&nbsp;&nbsp;</td><td valign="baseline"> An 
<a href="ref-glossary.html#id70">extended&nbsp;unit-class&nbsp;or&nbsp;instance&nbsp;specification</a> 
(see below; default i