A language processing system uses annotation services that are external to the language processing system to identify n-grams that identify entities in an input sentence. The n-grams are annotated by the annotation services. The annotations are used to determine which n-grams, if any, correspond to instances of an entity type (e.g., values for a variable or terminals for a non-terminal). After determining which n-grams correspond to entity types, parse initializations are generated for parsing rules and parses for each rule are attempted. The rules that successfully parse are used to determine whether the input sentence invokes a specific action, and if so, what arguments are to be passed to the invocation of the action.