-# invoked in the Toroid, when the list of attributes is emitted; but
-# we can't test for 5=100 here, as the Bath Profile says to do, and
-# then use that as justification for emitting 5=3 in the Toroid.
+# invoked in the Toroid, when the list of attributes is emitted; we
+# test for we can't test for 5=100 here, as the Bath Profile says to
+# do, and rather optimistically use that as justification for emitting
+# t=l,r in the Toroid (which means that individual queries can request
+# either left- or right-truncation using "?".
+#
+# Finally, we also make a test for "X-isbn", an ISBN number search,
+# which is not actually in the Bath Profile. This gives us something
+# to back down to when the more general Standard Identifier search
+# isn't supported.