This library is a re-implementation of the SeqEval library. It is built with a focus on performance and soudness.

SCHEMES

The current schemes are supported:

• IOB1: Here, I is a token inside a chunk, O is a token outside a chunk and B is the beginning of the chunk immediately following another chunk of the same named entity.
• IOB2: It is same as IOB1, except that a B tag is given for every token, which exists at the beginning of the chunk.
• IOE1: An E tag used to mark the last token of a chunk immediately preceding another chunk of the same named entity.
• IOE2: It is same as IOE1, except that an E tag is given for every token, which exists at the end of the chunk.
• BILOU/IOBES: 'E' and 'L' denotes Last or Ending character in a sequence and 'S' denotes a single element and 'U' a unit element.

The BILOU and IOBES schemes are only supported in strict mode.

More information about schemes

• Wikipedia
• Article, chapter 2

Terminology

This library partially reuses the terminology of the SeqEval library. The concepts might not be mapped one to one.

• A class is an entity we are interested in, such as 'LOC' for location, 'PER' for person, 'GEO' for geography, etc. It can be anything.
• A token is a string containing a class, such a GEO, LOC, PER and a prefix. The prefix indicates where we are in the current chunk. For a given scheme, the list of possible prefix are the letters of the scheme, such as I-O-B or I-O-E. Prefix can only be a single ascii character.
• A chunk is list of at least one token associated with a named entity.
• A Scheme gives us enough information to parse a list of tokens into a chunk.