ClearTK was originally developed by the University of Colorado’s Center for Computational Language and Education Research.


Most of ClearTK is distributed under the BSD license.

However, a small portion of the code is licensed under the GPL because it depends on GPL licensed third party libraries. This code has been isolated into sub-projects so that only these sub-projects need to be licensed with the GPL. For further details on the software licenses please see:


If you use ClearTK to support academic research, please cite:

  author = {Steven Bethard and Philip Ogren and Lee Becker},
  title = {ClearTK 2.0: Design Patterns for Machine Learning in UIMA},
  booktitle = {Proceedings of the Ninth International Conference on Language Resources and Evaluation (LREC'14)},
  year = {2014},
  month = {5},
  date = {26-31},
  address = {Reykjavik, Iceland},
  publisher = {European Language Resources Association (ELRA)},
  pages = {3289--3293},
  url = {http://www.lrec-conf.org/proceedings/lrec2014/pdf/218_Paper.pdf}}

If you use the ClearTK-TimeML modules, please cite:

  author    = {Bethard, Steven},
  title     = {ClearTK-TimeML: A minimalist approach to !TempEval 2013},
  booktitle = {Second Joint Conference on Lexical and Computational Semantics (`*`SEM), Volume 2: Proceedings of the Seventh International Workshop on Semantic Evaluation (!SemEval 2013)},
  month     = {June},
  year      = {2013},
  address   = {Atlanta, Georgia, USA},
  publisher = {Association for Computational Linguistics},
  pages     = {10--14},
  url       = {http://www.aclweb.org/anthology/S13-2002}}