index terms are spread through the whole document and marked-up
by indexterm
element
<para>Wealth of a modern societies is built upon information<indexterm><primary>information</primary> </indexterm>.</para>
index terms can be multi-level and there are also other ways to mark them up
<indexterm> <primary>information</primary> </indexterm> ... <indexterm> <primary>information</primary> <secondary>retrieval</secondary> </indexterm> ... <indexterm> <primary>information</primary> <secondary>dissemination</secondary> </indexterm> ... <indexterm> <primary>information</primary> <secondary>dissemination</secondary> <tertiary>oral</tertiary> </indexterm>
sample output:
information, 13
dissemination, 17
oral, 25
retrieval, 15