1. A confidence computing method, comprising performing the following by a processor of a computer: (a) generating a syntactical parse tree for an interpreted text string, the parse tree including a plurality of sub-trees, each of the sub-trees representing a corresponding section of the interpreted text string; (b) for each of at least one of the plurality of sub-trees: extracting at least one feature of the respective sub-tree; and determining whether the respective sub-tree is accurate, the accuracy determination including: computing a respective confidence score characterizing a probability of the respective sub-tree's accuracy, the confidence score being computed using a statistical model into which the at least one extracted feature is input; and determining whether the respective confidence score meets a predetermined threshold value, wherein: the respective sub-tree is determined to be accurate if it is determined that the respective sub-tree's confidence score meets the threshold value; and the respective sub-tree is otherwise determined to be inaccurate; and (c) subsequent to a determination, for at least one of the sub-trees, that the at least one sub-tree is accurate, providing an output based on the at least one sub-tree's at least one corresponding section of the interpreted text string; wherein the at least one feature includes a history score which includes, for each of at least one child sub-tree of the respective sub-tree, the respective child sub-tree's previously computed confidence score.