1 Introduction
Temporal event data is nearly ubiquitous in this era of mobile devices, electronic communication, and sensor networks. It can be found in everything from social network activity, to financial transactions, to electronic health records. More than ever before, large collections of this sort of data are being recorded that capture (a) what type of event is happening, (b) when it happens, and (c) the entities (e.g., customer, bank account, or patient) involved.