1. A method, comprising: maintaining an online grammar model used by an online voice-based query processor to parse online voice-based queries, the online grammar model mapping a plurality of queries to actions, wherein the actions include non-search actions performable by a computer system, wherein each of the actions is mapped in the grammar model to one or more corresponding queries of the plurality of queries, and wherein each of a plurality of the actions includes one or more corresponding parameters for constraining performance of the action; analyzing query usage data for at least a subset of the plurality of queries to identify a subset of popular queries from among the plurality of queries mapped by the online grammar model, wherein the query usage data includes query usage data collected for queries issued by a plurality of users; and building an offline grammar model that maps the subset of popular queries to actions among the actions for use by a resource-constrained offline device, wherein the offline grammar model has reduced resource requirements relative to the online grammar model and omits mappings for one or more queries among the plurality of queries.