The Common Annotation,Tagging and Citation at Harvard project developed a cloud-based working prototype of the Annotation Hub (AH) database and an API. The AH enables storing, searching, discovering, sharing and analyzing scholarly annotations and tags (including semantic tagging) produced on four digital media types: text, image, audio and video. It is designed to interoperate with third-party annotation tools to aggregate and associate contextualized annotation metadata from various pedagogical and research tools with reference to persistent digital media in repositories, such as the Harvard Library DRS.