Latent Tree Models for Hierarchical Topic Detection
This addresses the problem of discovering meaningful topic hierarchies in document collections for researchers and practitioners in natural language processing, though it appears incremental as it builds on existing graphical models.
The paper tackles hierarchical topic detection by proposing hierarchical latent tree models (HLTMs) that cluster documents using binary latent variables to represent word co-occurrence patterns, resulting in a tree structure that yields thematically general to specific topics without relying on document generation processes.
We present a novel method for hierarchical topic detection where topics are obtained by clustering documents in multiple ways. Specifically, we model document collections using a class of graphical models called hierarchical latent tree models (HLTMs). The variables at the bottom level of an HLTM are observed binary variables that represent the presence/absence of words in a document. The variables at other levels are binary latent variables, with those at the lowest latent level representing word co-occurrence patterns and those at higher levels representing co-occurrence of patterns at the level below. Each latent variable gives a soft partition of the documents, and document clusters in the partitions are interpreted as topics. Latent variables at high levels of the hierarchy capture long-range word co-occurrence patterns and hence give thematically more general topics, while those at low levels of the hierarchy capture short-range word co-occurrence patterns and give thematically more specific topics. Unlike LDA-based topic models, HLTMs do not refer to a document generation process and use word variables instead of token variables. They use a tree structure to model the relationships between topics and words, which is conducive to the discovery of meaningful topics and topic hierarchies.