Annotating is a method by which scholars across disciplines organize existing knowledge and facilitate the creation and sharing of new knowledge. Annotating is used by individual scholars when reading as an aid to memory, to add commentary, and to classify. Annotations can facilitate shared editing, scholarly collaboration, and pedagogy. Over time personal notes and annotations can have scholarly value in their own right as compelling forms of evidence for historians and others studying the evolution of scholarly thinking. The work of the OAC (Open Annotation Collaboration) focuses on enabling annotation sharing and interoperability through the promulgation of data models and guidelines supporting the development of tools and services allowing scholars working in disparate locations to share and leverage annotations of digital resources across the boundaries of individual annotation applications and content collections.