Joint User- and Event- Driven Stable Social Event Organization.

The problem of social event organization (SEO) rises with the advent of online web services and plays an important role in helping users discover new offline events. Existing work on SEO only assumes that different users have different preferences towards different events, ignoring the fact that each event (its organizer) may have a separate preference towards every user. In this paper, we investigate joint user- and event- driven SEO by simultaneously considering user preferences (towards events) and event preferences (towards users). A risen challenging problem is that this joint consideration may suffer instabilities between users and events which are NP-hard to handle in SEO. Stability is a desired property that needs to be maintained in SEO, otherwise participants will incline towards changing to other events and trust less the organizer. To the best of our knowledge, we are the first to study SEO with both preferences from users to events and preferences from events to users being considered. In this work, we formulate the stable social event organization (Stable-SEO) problem and prove its NP-hardness. We then propose an efficient greedy heuristic algorithm to solve Stable-SEO, taking both user preferences and event preferences into account. The proposed approach is able to find an assignment of a group of users to a set of events for an event organization, in which there is a minimized number of users involved in user-event pairs such that both the user and event in one such pair will be better off when reassigning the user to this event. Our experiments on two real-world datasets demonstrate the strong superiority of our proposed approach over existing methods.