Funnelling
(
Fun
) is a recently proposed method for cross-lingual text classification (CLTC) based on a two-tier learning ensemble for heterogeneous transfer learning (HTL). In this ensemble method, 1st-tier classifiers, each working on a different and language-dependent feature space, return a vector of calibrated posterior probabilities (with one dimension for each class) for each document, and the final classification decision is taken by a meta-classifier that uses this vector as its input. The meta-classifier can thus exploit class-class correlations, and this (among other things) gives
Fun
an edge over CLTC systems in which these correlations cannot be brought to bear. In this paper we describe
Generalized Funnelling
(
gFun
), a generalisation of
Fun
consisting of an HTL architecture in which 1st-tier components can be arbitrary
view-generating functions
, i.e., language-dependent functions that each produce a language-independent representation (“view”) of the (monolingual) document. We describe an instance of
gFun
in which the meta-classifier receives as input a vector of calibrated posterior probabilities (as in
Fun
) aggregated to other embedded representations that embody other types of correlations, such as word-class correlations (as encoded by
Word-Class Embeddings
), word-word correlations (as encoded by
Multilingual Unsupervised or Supervised Embeddings
), and word-context correlations (as encoded by
multilingual BERT
). We show that this instance of
gFun
substantially improves over
Fun
and over state-of-the-art baselines, by reporting experimental results obtained on two large, standard datasets for multilingual multilabel text classification. Our code that implements
gFun
is publicly available.