1. A method in a computer system for parsing input in a language, the language having a grammar described by syntax rules, each syntax rule having a probability indicating a likelihood that the syntax rule will lead to a final parse of the input, the method comprising repeating the following until the final parse is generated: selecting a syntax rule to apply to a current partial parse of the input, the selected syntax rule having a high probability relative to other syntax rules that can be applied to the current partial parse of the input; applying the selected syntax rule to the current partial parse of the input to form a new current partial parse of the input; determining whether syntax rules with low probabilities have been recently applied; and when it is determined that syntax rules with low probabilities have recently been applied, disabling application of syntax rules to a portion of the current partial parse of the input so that that syntax rule application can be focused on the other portion of the current partial parse of the input.