Patterns with features

Each PoS tag in a pattern may contain morpho-syntactic and/or lexical information. This information is represented by a feature-value structure, noted as a pair <feature:value>. Let's see some examples:
ADV<lemma:very> ADV

PRO<type:R> VERB

The first pattern represents a dependency between two adverbs, one of them is associated to the lemma ``very''. This is a lexical restriction. The second pattern represents a dependency between a pronoun and a verb. The pronoun is characterized by means of the type ``R(elative)''. This is a morpho-syntactic restriction. Both lexical and morpho-syntactic restrictions are represented by means of feature-value structures. In the example above, ``lemma'' and ``type'' are features, while ``very'' and ``R'' are their specific values.

One of the main advantages of DepPattern is that features are only used when they are necessary. Given a PoS tag, all those features that are not specified in a pattern are considered to have value 0.



Pablo Gamallo 2009-09-14