This article has multiple issues. Please help improve it or discuss these issues on the talk page. (Learn how and when to remove these template messages)(Learn how and when to remove this template message)
The IOB format (short for inside, outside, beginning) is a common tagging format for tagging tokens in a chunking task in computational linguistics, (ex. named-entity recognition). It was presented by Ramshaw and Marcus in their paper "Text Chunking using Transformation-Based Learning", 1995  The B- prefix before a tag indicates that the tag is the beginning of a chunk, and an I- prefix before a tag indicates that the tag is inside a chunk. The B- tag is used only when a tag is followed by a tag of the same type without O tokens between them. An O tag indicates that a token belongs to no chunk.
Another similar format which is widely used is IOB2 format, which is the same as the IOB format with the difference that the B- tag is used in the beginning of every chunk (i.e. all chunks start with the B- tag).
A readable introduction to entity tagging is given in Bob Carpenter's blog post, "Coding Chunkers as Taggers". 'BIO' is plausibly a synonym for 'IOB'.
- "Entity Recognition".
- Ramshaw and Marcus (1995). "Text Chunking using Transformation-Based Learning". arXiv: .
- Bob Carpenter (2009). "Coding Chunkers as Taggers: IO, BIO, BMEWO, and BMEWO+".
|This computational linguistics-related article is a stub. You can help Wikipedia by expanding it.|