  Prior work on personalized recommendations has focused on exploiting explicit
signals from user-specific queries, clicks, likes, and ratings. This paper
investigates tapping into a different source of implicit signals of interests
and tastes: online chats between users. The paper develops an expressive model
and effective methods for personalizing search-based entity recommendations.
User models derived from chats augment different methods for re-ranking entity
answers for medium-grained queries. The paper presents specific techniques to
enhance the user models by capturing domain-specific vocabularies and by
entity-based expansion. Experiments are based on a collection of online chats
from a controlled user study covering three domains: books, travel, food. We
evaluate different configurations and compare chat-based user models against
concise user profiles from questionnaires. Overall, these two variants perform
on par in terms of NCDG@20, but each has advantages in certain domains.
