xindy is an index processor that can be used to generate book-like
indexes for arbitrary document-preparation systems. This includes
systems such as TeX and LaTeX, the roff-family, SGML/XML-based
systems (e.g. HTML) that process some kind of text and generate
indexing information. The kernel system is not fixed to any specific
system, but can be configured to work together with such systems.

In comparison to other index processors xindy has several powerful
features that make it an ideal framework for describing and
generating complex indices, addressing especially international
indexing.