The Complexity Intelligence Part Of Speech Tagging API looks at a sentence, or a set of sentences, analyzes them and marks up each word in a text with an identifier of a semantic class (part of speech). Complexity Intelligence is a start-up that focuses on Artificial Intelligence research. Complexity Intelligence is developing a range of natural language processing services accessible through web-services. Both free and paid subscriptions are available. Support is provided for both Java and PHP. The API uses RESTful protocol and responses are formatted in XML.