IXA pipes modules consist of: (i) Local, shallow features based mostly on orthographic, word shape and n-gram features plus their context; and (ii) three types of simple clustering features, based on unigram matching.
iXA pipes implements, on top of the local features, a combination of three word representation features: (i) Brown (Brown et al., 1992) clusters, taking the 4th, 8th, 12th and 20th node in the path; (ii) Clark (Clark, 2003) clusters and, (iii) Word2vec (Mikolov et al., 2013) clusters, based on K-means applied over the extracted word vectors using the skip-gram algorithm.