Word-Graph-Based Handwriting Keyword Spotting of Out-of-Vocabulary Queries

Thanks to the use of lexical and syntactic information, Word Graphs (WG) have shown to provide a competitive Precision-Recall performance, along with fast lookup times, in comparison to other techniques used for Key-Word Spotting (KWS) in handwritten text images. However, a problem of WG approaches is that they assign a null score to any keyword that was not part of the training data, i.e. Out-of-Vocabulary (OOV) keywords, whereas other techniques are able to estimate a reasonable score even for these kind of keywords. We present a smoothing technique which estimates the score of an OOV keyword based on the scores of similar keywords. This makes the WG-based KWS as flexible as other techniques with the benefit of having much faster lookup times.