Context Mover's Distance & Barycenters: Optimal Transport of Contexts for Building Representations
This approach addresses the problem of capturing uncertainty and polysemy in text representations for NLP researchers, offering interpretability and applicability on top of existing methods, though it is incremental in its use of optimal transport for a known bottleneck.
The paper tackles unsupervised representation learning by modeling entities as probability distributions over contexts, using optimal transport tools like Wasserstein distance and barycenters, resulting in significant gains such as a 4.1% relative improvement over methods like Sent2vec and GenSen on tasks like sentence similarity and word entailment.
We present a framework for building unsupervised representations of entities and their compositions, where each entity is viewed as a probability distribution rather than a vector embedding. In particular, this distribution is supported over the contexts which co-occur with the entity and are embedded in a suitable low-dimensional space. This enables us to consider representation learning from the perspective of Optimal Transport and take advantage of its tools such as Wasserstein distance and barycenters. We elaborate how the method can be applied for obtaining unsupervised representations of text and illustrate the performance (quantitatively as well as qualitatively) on tasks such as measuring sentence similarity, word entailment and similarity, where we empirically observe significant gains (e.g., 4.1% relative improvement over Sent2vec, GenSen). The key benefits of the proposed approach include: (a) capturing uncertainty and polysemy via modeling the entities as distributions, (b) utilizing the underlying geometry of the particular task (with the ground cost), (c) simultaneously providing interpretability with the notion of optimal transport between contexts and (d) easy applicability on top of existing point embedding methods. The code, as well as prebuilt histograms, are available under https://github.com/context-mover/.