In many real-world applications, there are multiple dialog types in human-bot conversations (called multi-type dialogs), such as chit-chat, task oriented dialogs, recommendation dialogs, and even question answering (Ram et al., 2018;Wang et al., 2014;Zhou et al., 2018b).
it is crucial to study how to proactively and naturally make conversational recommendation by the bots in the context of multi-type human-bot communication.