TIP-tree: A spatial index for traversing locations in context-aware mobile access to digital libraries

We present a spatial index called the TIP-tree, for efficient, uniform, location-based access to digital library collections that are external sources to a context-aware mobile system. Using a tourist information system, we also utilize the TIP-tree to manage the context of location. We show how access to resources from within and outside of the tourist information system can be carried out seamlessly. We also propose a strategy to show how the TIP-tree can be navigated within the structure itself to continually provide information to the user. An empirical evaluation of the navigation strategy with both synthetic and real data shows that navigation is very efficient, with a constant number of node accesses regardless of data and trajectory size, and at least an 80% improvement in node accesses over searching with other spatial indexing approaches.