Models and Tools for Collaborative Annotation
  The Annotation Graph Toolkit (AGTK) is a collection of software which facilitates development of linguistic annotation tools. AGTK provides a database interface which allows applications to use a database server for persistent storage. This paper discusses various modes of collaborative annotation and how they can be supported with tools built using AGTK and its database interface. We describe the relational database schema and API, and describe a version of the TableTrans tool which supports collaborative annotation. The remainder of the paper discusses a high-level query language for annotation graphs, along with optimizations, in support of expressive and efficient access to the annotations held on a large central server. The paper demonstrates that it is straightforward to support a variety of different levels of collaborative annotation with existing AGTK-based tools, with a minimum of additional programming effort. 
Xiaoyi Ma, Haejoong Lee, Steven Bird and Kazuaki Maeda