OpenCalais is a suite of web-based text analytics tools designed to support the semantic web. It includes NLP utilities for entity extraction and event/fact extraction, as well as some grammatical capabilities. Its services are provided through web service calls.

Prajna extensions include an implementation of an OpenCalais-based entity extractor. This extractor sends the text to the OpenCalais engine, parses the results, and transforms them into a format that conforms to Prajna's entity extraction interface.

OpenCalais requires a license key to use. Developers may request a license key for free at the OpenCalais web site.

More capabilities will be added in the future.