Rapid, sustained advances in key computing technologies combine to enable a new class of computing services that aim to meet needs of mobile users. These ubiquitous and intelligent services adapt to each user's particular preferences and current circumstances---they are personalized. The services exploit data available from multiple sources, including data on past interactions with the users, data accessible via the Internet, and data obtained from sensors. The user's geographical location is particularly central to these services. We outline some of the research challenges that aim to meet the data representation and indexing needs of such services
