2. A method as recited in claim 1 , wherein the series of user input selections comprises a partial data input, and wherein the additional input selection is determined by: comparing, by the computer, the partial data input to a plurality of grammar rules that identify valid inputs; identifying by the computer, based on the comparing, a set of grammar rules that match the partial data input; assigning a score to each of the grammar rules by the computer, the score indicating how closely the grammar rule matches the partial data input; and selecting by the computer, as the additional input selection, the grammar rule with a highest score.
5. A method as recited in claim 2 , wherein at least one of the plurality of grammar rules includes a variable.