1. A system for automatically generating sentences in a language, comprising: at least one grammar processor for acquiring a grammar as input and creating a grammar hierarchy by converting said grammar into a hierarchical representation, wherein said grammar hierarchy includes a plurality of trees corresponding to a plurality of productions in said grammar; and at least one grammar explorer module for acquiring an exploration specification as input and exploring and traversing said grammar hierarchy based on a plurality of exploration types externally specified in said exploration specification, wherein said grammar explorer module generates a plurality of sentences of a language in accordance with said explored and traversed grammar hierarchy.