Triple Alliance Prototype Orthotist Network for Long-Tailed Multi-Label Text Classification

Abstract

Text classification, is one of the key tasks for representing the semantic information of documents, multi-label text classification (MLTC) is an important branch of it. MLTC aims to tag the most relevant labels for the given document. Compared to the standard multi-class case where each document has only one label, it is considerably more difficulty to annotate new coming documents for multi-label text classification. Furthermore, it also suffers from the challenge of highly skewed long-tailed label distribution. i.e., a few labels are associated with a large number of documents (a.k.a. head labels), while a large fraction of labels are associated with a small number of documents (a.k.a. tail labels). Due to the relative infrequency of tail labels, this leads to an imbalance that biases towards predicting more head labels. As challenging as this task is, it is an essential task to tackle since it represents many real-world cases, such as text retrieval of news. To address the challenge, we propose a Triple Alliance Prototype Orthotist Network (TAPON) to build a generic meta-mapping from few-shot prototypes to many-shot classifier parameters, which aims to promote the generalizability of tail classifiers. To be specific, TAPON is a two-stage method. At the first stage focusing on head labels, TAPON obtains the meta-knowledge between many-shot classifier parameters and few-shot prototype of head labels. Head label classifiers are trained by many-shot documents. Meanwhile, the triple alliance prototype is obtained by adopting an Attentive Prototype with the aid of few-shot documents, label semantic information and label correlation. Additionally, a Prototype Orthotist module is especially designed to capture the meta-knowledge between the many-shot classifier and few-shot prototype. At the second stage of transferring, TAPON aims to transfer the generic meta-mapping from head labels to tail labels. It first uses Attentive Prototype to obtain triple alliance prototype for tail labels, and then uses the meta-knowledge obtained from the first stage to get many-shot classifiers for tail labels. By conducting extensive experiments on four benchmark datasets, we show that the proposed TAPON significantly outperforms other state-of-the-art methods for long-tailed multi-label text classification.