Lemur Project

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The Lemur Project is a collaboration between the Center for Intelligent Information Retrieval at the University of Massachusetts Amherst and the Language Technologies Institute at Carnegie Mellon University. It develops the Lemur Toolkit, an open-source (BSD license) software framework for building language modeling and information retrieval software, and the Indri search engine. This toolkit is used for developing search engines, text analysis tools, browser toolbars, and data resources in the area of IR.

The programming languages used to create Lemur are C and C++ and it comes along with the source files and a make file. The provided source code can be modified for the purpose of developing new libraries. It is compatible with various operating systems which include UNIX (Linux and Solaris) and Windows XP.


Lemur supports the following features:

  • Indexing:
  • Retrieval:
    • Ad hoc retrieval (TF-IDF and InQuery)
    • Passage and cross-lingual retrieval
    • Language modeling
      • Query model updating
      • Two stage smoothing
    • Relevance feedback
    • Structured query language
    • Wildcard term matching
  • Distributed IR:
    • Query-based sampling
    • Database based ranking (CORI)
    • Results merging
  • Document clustering
  • Summarization
  • Simple text processing


Lemur Project has the following components:

  • Lemur Toolkit
  • Indri
  • Galago
  • Lemur Query Log Toolbar
  • ClueWeb09 Dataset

Latest Version[edit]

The latest version of the Indri search engine is 5.8.

The final and latest available version of the Lemur Toolkit is version 4.12.

Indri Search Engine[edit]

The Indri search engine is one of the components of the Lemur toolkit. It is open source as well. The query language that is used in Indri allows researchers to index data or structure documents using simple command line instructions. Indri offers flexibility in terms of adaptation to various current applications. It also can be distributed across a cluster of nodes for high performance. Indri search engine can handle large collections of data and can understand various data formats like HTML and XML.

The Indri API supports various programming and scripting languages like C++, Java, C#, and PHP. The latest available version of Indri is 5.6.

Features of Indri Search Engine[edit]

  • Can make use of multiple document representations
  • Explicit term weighting
  • Robust query language
  • Formally well-grounded
  • Highly effective
  • Can be efficiently implemented

See also[edit]

External links[edit]