The mystery was solved when I looked at the triples.txt file in the config subdirectory in the alice2 bot included with the Program AB download. In it are a series of lines containing three sets of words, each set separated by a colon. Among others, there are a series of lines about various animals. For example, there are lines like “bear:sound:grrrrr” and “bear:legs:4” and so on. There are similar lines for other animals. Note that there is also a set file containing the names of animals, each of which has its lines in the triples.txt file.
The tags in question are ways of referencing the lines for a particular animal and there are categories in animal.aiml which use these tags extensively. You could have several categories asking what sound a bear makes, all of which would be referenced by <srai> to a category having the pattern <pattern><set>animal</set></pattern> is
<template>bear says <uniq><subj></star></subj><pred>sound</pred><obj>?sound</obj></uniq></template>
The text editor will probably insert errors which can’t be removed in preview and if so I’ll add another reply for error correction.
The <subj> tag will reference the first word in the bear line and the <pred> tag will reference “sound”. The <obj> tag will ask for what is in the third line, which is “grrrrr”. The reply will be “bear says grrrrr”.