Houjun Liu

NER Tagging

while POS Tagging assigns tags to each word, NER Tagging tags the category of usage of multi-word spans.

NER Tagging needs to label spans of text, which means that there is ambiguity in type.

BIO Tagging

BIO Tagging will tag each word: where \(B\) begins a span, \(I\), is inside a span, and \(O\) outside a span. So tags per word still apply, but we can extract span information as well.

(job - gender + gender ) = job (captial - country + country) = captial