Automatic key extraction
From OpenKM Documentation
OpenKM uses KEA for extracting keyphrases from text documents. KEA it by default can be either used for free indexing or for indexing with a controlled vocabulary, but with OpenKM is mandatory having a controled vocabulary.
If order having KEA running in OpenKM must be a well done configured vocabulary (Thesaurus).
KEA is a training module that uses a Thesaurus as the controller vocabulary. In order how to configure OpenKM Thesaurus take a look at Thesaurus in installation guide.