Analysis of Textual Variation by Latent Tree Structures

We introduce Semstem, a new method for the reconstruction of so called stemmatic trees, i.e., trees encoding the copying relationships among a set of textual variants. Our method is based on a structural expectation-maximization (structural EM) algorithm. It is the first computer-based method able to estimate general latent tree structures, unlike earlier methods that are usually restricted to bifurcating trees where all the extant texts are placed in the leaf nodes. We present experiments on two well known benchmark data sets, showing that the new method outperforms current state-of-the-art both in terms of a numerical score as well as interpretability.