1. A voice-interactive dialog system for facilitating conversational speech across different domains, comprising: a phrase database storing (i) phrases grouped into equivalence classes and (ii) a probability of occurrence for each phrase within a corpus; wherein each equivalence class is associated with one or more domains; a user interface configured to allow interaction with an interactive part of the system; a recognition server coupled with the phrase database and the user interface and configured to: identify a user request upon receiving a user utterance via the user interface, wherein the user request is associated with a domain; formulate a system prompt in response to the user utterance, the prompt comprising a combination of one or more phrases from the phrase database that are associated with the domain; upon receiving a user response to the system prompt via the user interface, generate a recognition grammar from phrases in the phrase database that fall within an equivalent class associated with the user response; and generate a recommendation to the user via the user interface, wherein the recommendation is associated with the domain.