Question: What baseline models are used?
Answer: the Poly-encoder from BIBREF7 humeau2019real, Feed Yourself BIBREF13 is an open-domain dialogue agent with a self-feeding model, Kvmemnn BIBREF14 is a key-value memory network with a knowledge base that uses a key-value retrieval mechanism to train over multiple domains simultaneously, We compare against four dialogue system baselines: Kvmemnn, Feed Yourself, Poly-encoder, and a BERT bi-ranker baseline trained on the Persona-Chat dataset using the same training hyperparameters (including learning rate scheduler and length capping settings) described in Section SECREF20., a BERT bi-ranker
Alternative answer: Kvmemnn,  Feed Yourself, Poly-encoder, BERT bi-ranker