Obtaining a Better Understanding of Distributional Models of German Derivational Morphology

Predicting the (distributional) meaning of derivationally related words (read / read+er) from one another has recently been recognized as an instance of distributional compositional meaning construction. However, the properties of this task are not yet well understood. In this paper, we present an analysis of two such composition models on a set of German derivation patterns (e.g., -in, durch-). We begin by introducing a rank-based evaluation metric, which reveals the task to be challenging due to specific properties of German (compounding, capitalization). We also find that performance varies greatly between patterns and even among base-derived term pairs of the same pattern. A regression analysis shows that semantic coherence of the base and derived terms within a pattern, as well as coherence of the semantic shifts from base to derived terms, all significantly impact prediction quality.