  Proactive dialogue systems, related to a wide range of real-world
conversational applications, equip the conversational agent with the capability
of leading the conversation direction towards achieving pre-defined targets or
fulfilling certain goals from the system side. It is empowered by advanced
techniques to progress to more complicated tasks that require strategical and
motivational interactions. In this survey, we provide a comprehensive overview
of the prominent problems and advanced designs for conversational agent's
proactivity in different types of dialogues. Furthermore, we discuss challenges
that meet the real-world application needs but require a greater research focus
in the future. We hope that this first survey of proactive dialogue systems can
provide the community with a quick access and an overall picture to this
practical problem, and stimulate more progresses on conversational AI to the
next level.
