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.