Tagger

Definition

A tagger is a device which assigns symbolic labels (tags) to linguistics units. The labels are taken from a predefined set of symbols (tag-set).

Comments

In most cases, a tagger assigns tags representing morpho-syntactic information to single word-forms or token. But there are tagger which have been designed to identify semantic role of noun phrases or prepositional phrases (sense tagging) and sometimes identiying the discourse structure of a text is considered as a king of tagging.

Conceptually, tagging can be considered as a three step process: (i). identification of the relevant units (ii). assigning all possible labels to the units (e.g. by lexical look-up, applying heuristics, etc.) (iii). disambiguation.

It is common practice to distinguish between rule-based and stochastic tagger, though some tagger combine rules and stochastic information.

State-of-the-art tagger achieve a precision of at least 95% for morpho-syntactic tagging.

Subtypes

• Brill tagger
• HMM tagger
• Memory-based tagger
• Tree tagger

Other Languages

• German Tagger (de)