Evaluating Unsupervised Text Classification: Zero-shot and Similarity-based Approaches
Authors: Tim Schopf, Daniel Braun, Florian Matthes
AI-generated Key Points
- Text classification of unseen classes is a significant challenge in Natural Language Processing.
- Two main types of methods used for this task are similarity-based approaches and zero-shot text classification approaches.
- Existing literature lacks consistent comparisons between these two types of methods.
- A systematic evaluation was conducted in the study on different similarity-based and zero-shot text classification methods for unseen classes.
- Benchmarking various state-of-the-art approaches was done on four text classification datasets, including a new dataset from the medical domain.
- Novel baselines using SimCSE and SBERT embeddings were proposed to improve results.
- A new similarity-based approach called Lbl2TransformerVec was introduced and outperformed existing state-of-the-art methods in unsupervised text classification tasks.
- Similarity-based approaches generally outperformed zero-shot methods across most cases in the experiments.
- Advanced embeddings like SimCSE or SBERT led to further improvements in similarity-based classification results compared to simpler text representations.
Abstract: Text classification of unseen classes is a challenging Natural Language Processing task and is mainly attempted using two different types of approaches. Similarity-based approaches attempt to classify instances based on similarities between text document representations and class description representations. Zero-shot text classification approaches aim to generalize knowledge gained from a training task by assigning appropriate labels of unknown classes to text documents. Although existing studies have already investigated individual approaches to these categories, the experiments in literature do not provide a consistent comparison. This paper addresses this gap by conducting a systematic evaluation of different similarity-based and zero-shot approaches for text classification of unseen classes. Different state-of-the-art approaches are benchmarked on four text classification datasets, including a new dataset from the medical domain. Additionally, novel SimCSE and SBERT-based baselines are proposed, as other baselines used in existing work yield weak classification results and are easily outperformed. Finally, the novel similarity-based Lbl2TransformerVec approach is presented, which outperforms previous state-of-the-art approaches in unsupervised text classification. Our experiments show that similarity-based approaches significantly outperform zero-shot approaches in most cases. Additionally, using SimCSE or SBERT embeddings instead of simpler text representations increases similarity-based classification results even further.
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