Reuters has released an open API for its new Calais Web service that aims to make it easier for publishers, bloggers, and other content producers to automatically metatag their content and to develop their own applications for the Semantic Web. To use the service, a publisher simply inputs unstructured text and the service returns semantic metadata in RDF format in less than a second. Using natural-language processing and machine learning techniques, Calais locates entities, facts, and events and processes those components into metadata. “Publishers can use this information as auxiliary tags for their content to improve searchability, they can use it to enhance news feeds with better tagging, or any number of other purposes,” said another executive. Here's the scoop.