Abstract: A method of automatically imputing missing or erroneous data. The method comprises dividing a portion of input data (e.g. a sentence) into a sequence of smaller elements (e.g. words), and identifying points in the sequence at which missing or erroneous data is potentially to be imputed. For each point, a first search step generates a respective set of one or more paths for the respective point, each path comprising a candidate element to potentially replace the missing or erroneous data at the respective point, and an associated probability score generated by a neural network. In each subsequent search step for each point, a set of one or more of the preceding paths from one or more of the preceding search steps are selected to extend with an additional candidate element and score again. The paths are compared from across the different search steps to select at least one for output.