One of the travelers’ main challenges is that they have to spend a great effort to find and
choose the most desired travel offer(s) among a vast list of non-categorized and non-personalized
items. Recommendation systems provide an effective way to solve the problem of information
overload. In this work, we design and implement “The Hybrid Offer Ranker” (THOR), a hybrid,
personalized recommender system for the transportation domain. THOR assigns every traveler a
unique contextual preference model built using solely their personal data, which makes the model
sensitive to the user’s choices. This model is used to rank travel offers presented to each user
according to their personal preferences. We reduce the recommendation problem to one of binary
classification that predicts the probability with which the traveler will buy each available travel
offer. Travel offers are ranked according to the computed probabilities, hence to the user’s personal
preference model. Moreover, to tackle the cold start problem for new users, we apply clustering
algorithms to identify groups of travelers with similar profiles and build a preference model for each
group. To test the system’s performance, we generate a dataset according to some carefully designed
rules. The results of the experiments show that the THOR tool is capable of learning the contextual
preferences of each traveler and ranks offers starting from those that have the higher probability of
being selected