ATLAS was originally based on the LDC research on Annotation Graphs (also known as ATLAS Level 0). Annotation Graphs provide a data model for working with linear signals (such as text and audio) indexed by intervals. Annotation Graphs are a limited sub-set of the more generic ATLAS data model.
Considering the need to create an annotation framework capable of handling more complex signals, NIST pushed forward to extend the Annotation Graph formalism. A first implementation of the generalized model was released in April 2001.
Based on the feedback that we received about the first implementation, we decided to go back to our drawing boards to provide better handling of hierarchical structures. We also introduced the concept of Meta-Annotation that allows users to adapt the generic data model to their specific needs without having to write a single line of code!
This web site deals only with ATLAS. For more information on Annotation Graphs, please see the Annotation Graphs page at the LDC. Annotation Graphs and ATLAS differ in their philosophy in that Annotation Graphs are optimized for simple annotations of audio signals while ATLAS focuses on genericness and extensibility and is not constrained to a given class of signals.