ExtrAns is a system that finds answers to questions about (the Solaris variety of) UNIX in the on-line system documentation, the manpages. The questions may be phrased in ordinary English rather than in some formal query language. The answers are the sentence(s) of the manpages containing direct answers to the question (if there are any), complete with clickable links into the full manpages containing them.

ExtrAns is an experimental system intended to test the concept of Answer Extraction (AE) over one particular text, and in one particular language. It is still under development, and it is very far from being perfect. However, we like to think that it is already considerably better than the various search engines available today. These engines normally use the techniques developed in Information Retrieval (IR), which are ultimately keyword based. In contrast, AE tries to use as much of the linguistic information contained in both questions and texts as possible.

In particular, it is the grammatical dependencies between the words in a sentence and, ultimately, the meaning expressed through these dependencies which are used to find relevant portions of the documents. Clearly, we can model only a minute part of the entire meaning of sentences but still, retrieval is very precise. Recall is still lower than for IR standard systems, which is why we added a capability for graceful degradation at the end of which IR retrieval methods are used.

This demo of ExtrAns uses the first three sections of the 500+ UNIX manpages. It finds portions of text that contain the answer to a query in explicit form. This means in particular that the system does not perform any kind of inferences to find information implicitly contained in the text. Finally, the system is not a dialogue system, and it forgets about a question and the answers the very moment it writes them on the screen.

  • ExtrAns Demo
  • How to Ask ExtrAns
  • Technical Background of ExtrAns
  • Press Releases
  • Everybody is welcome to work with ExtrAns and put the system through its paces. Whenever you have any suggestions for improvement, we would like to hear from you. If ExtrAns has convinced you and you would like to use this tool in a commercial product, please contact us.

    More Information

    More information on ExtrAns, complete with pointers to publications, can be found on the ExtrAns Project Page.

    [Computational Linguistics]   2.3.2000 / Rolf Schwitter