  Current conversational systems can follow simple commands and answer basic
questions, but they have difficulty maintaining coherent and open-ended
conversations about specific topics. Competitions like the Conversational
Intelligence (ConvAI) challenge are being organized to push the research
development towards that goal. This article presents in detail the RLLChatbot
that participated in the 2017 ConvAI challenge. The goal of this research is to
better understand how current deep learning and reinforcement learning tools
can be used to build a robust yet flexible open domain conversational agent. We
provide a thorough description of how a dialog system can be built and trained
from mostly public-domain datasets using an ensemble model. The first
contribution of this work is a detailed description and analysis of different
text generation models in addition to novel message ranking and selection
methods. Moreover, a new open-source conversational dataset is presented.
Training on this data significantly improves the Recall@k score of the ranking
and selection mechanisms compared to our baseline model responsible for
selecting the message returned at each interaction.
