HTMOT : Hierarchical Topic Modelling Over Time
This addresses the need for more detailed and time-sensitive topic analysis in text corpora, though it is incremental by combining existing concepts of hierarchy and temporality.
The authors tackled the problem of jointly modeling topic temporality and hierarchy in topic modeling, proposing HTMOT, which efficiently extracts accurate high-level themes and temporally precise sub-topics, as demonstrated in a case study on the 2020 space industry.
Over the years, topic models have provided an efficient way of extracting insights from text. However, while many models have been proposed, none are able to model topic temporality and hierarchy jointly. Modelling time provide more precise topics by separating lexically close but temporally distinct topics while modelling hierarchy provides a more detailed view of the content of a document corpus. In this study, we therefore propose a novel method, HTMOT, to perform Hierarchical Topic Modelling Over Time. We train HTMOT using a new implementation of Gibbs sampling, which is more efficient. Specifically, we show that only applying time modelling to deep sub-topics provides a way to extract specific stories or events while high level topics extract larger themes in the corpus. Our results show that our training procedure is fast and can extract accurate high-level topics and temporally precise sub-topics. We measured our model's performance using the Word Intrusion task and outlined some limitations of this evaluation method, especially for hierarchical models. As a case study, we focused on the various developments in the space industry in 2020.