The basic job done by regain is: The crawler searches for documents, extracts their text and stores it in a search index. Using this index, the search mask can answer search queries from users in nearly no time. For writing and using the search index, regain is using a library called Lucene.

The most important components of regain are:

• crawler - It searches for documents and extracts their text using the preparator.
• search index - The search index is bunch of files which are used by Lucene for answering search queries.
• search mask - The search mask shows a web user interface to the user where he can enter search queries and browse through the results. The web pages are rendered using the search mask jsp pages.