 Traditional NER assume that each entity type is an independent class.  However, they can have a hierarchical structure

 All models are based on MEMM classifier  Model 1 ◦ Just take the ancestor types to be features  Model 2 ◦ Train a classifier at each level ◦ Do verterbi on paths in the tree

 Every node in the tree has a local weight and global weight  Global weight is for classification. ◦ The sum of the local weights from the root to the node  Example

 Thanks David and Mihai for insightful discussions  Thanks instructors for excellent courses  Thanks TAs for hard work.