XCDE - Xml Compressed Document Engine The XCDE Library is a native system to compress and index XML files. It uses inverted list and tagstruct to support proximity and structural queries. http://butirro.di.unipi.it/~ferrax/xcde/xcdelib.html

Lucene Search Engine Jakarta Lucene is a full-featured text search engine written entirely in Java, and it is an open source project available for free download from Apache Jakarta. The current goals of the project are primarily to provide application and also a platform for research. http://jakarta.apache.org/lucene/