Mailing the story:

The Strigi project is the core of the index and search technology for KDE 4. Strigi is designed to be small and fast, and it can be installed and used with or without KDE 4, as we'll see. Strigi uses plugins to handle its indices, filetypes, and metadata extraction. Currently the filesystem index can be stored in SQLite 3, Xapian, CLucene and Hyper Estraier. The filetype plugins allow Strigi to get at the text content of non plain text files, such as PDF or office file formats. The metadata extraction plugins can tell Strigi information about files -- for example, the ID3 metadata tags from audio files.