Xapian is an Open Source Probabilistic Information Retrieval library,
released under the GPL. It's written in C++, with bindings to allow use
from other languages.

Xapian is designed to be a highly adaptable toolkit to allow developers to
easily add advanced indexing and search facilities to their own
applications.

Xapian features include:
 - Ranked probabilistic search - word importance weighting
 - Relevance feedback
 - Phrase and proximity searching
 - Full range of structured boolean search operators
 - Term stemming
 - Database files > 2GB
 - Platform independent data formats
 - Allows simultaneous update and searching.

WWW: http://www.xapian.org
