Learning Dynamic Contextualised Word Embeddings via Template-based Temporal Adaptation
This work addresses the challenge of modeling word meaning shifts over time for natural language processing applications, representing an incremental improvement with specific gains in performance.
The paper tackles the problem of learning dynamic contextualised word embeddings to capture temporal semantic changes, proposing a template-based method for adapting pretrained language models to new time periods, which reduces perplexity on test sentences and outperforms current state-of-the-art methods.
Dynamic contextualised word embeddings (DCWEs) represent the temporal semantic variations of words. We propose a method for learning DCWEs by time-adapting a pretrained Masked Language Model (MLM) using time-sensitive templates. Given two snapshots $C_1$ and $C_2$ of a corpus taken respectively at two distinct timestamps $T_1$ and $T_2$, we first propose an unsupervised method to select (a) \emph{pivot} terms related to both $C_1$ and $C_2$, and (b) \emph{anchor} terms that are associated with a specific pivot term in each individual snapshot. We then generate prompts by filling manually compiled templates using the extracted pivot and anchor terms. Moreover, we propose an automatic method to learn time-sensitive templates from $C_1$ and $C_2$, without requiring any human supervision. Next, we use the generated prompts to adapt a pretrained MLM to $T_2$ by fine-tuning using those prompts. Multiple experiments show that our proposed method reduces the perplexity of test sentences in $C_2$, outperforming the current state-of-the-art.