Multimodal Interactive Parsing

Probabilistic parsing is a fundamental problem in Computational Linguistics, whose goal is obtaining a syntactic structure associated to a sentence according to a probabilistic grammatical model. Recently, an interactive framework for probabilistic parsing has been introduced, in which the user and the system cooperate to generate error-free parse trees. In an early prototype developed according to this interactive parsing technology, user feedback was provided by means of mouse actions and keyboard strokes. Here we augment the interaction style with support for (non-deterministic) natural handwritten recognition, and provide confidence measures as a visual aid to ease the correction process. Handwriting input seems to be a modality specially suitable for parsing, since the vocabulary size involved in the recognition of syntactic labels is fairly limited and thus intuitively errors should be small. However, errors may increase as handwriting quality (i.e., calligraphy) degrades. To solve this problem, we introduce a late fusion approach that leverages both on-line and off-line information, corresponding to pen strokes and contextual information from the parse trees. We demonstrate that late fusion can effectively help to disambiguate user intention and improve system accuracy.