Abstract: In the last decade, mobile communication has enjoyed unprecedented growth all over the world. The recent advances in mobile communication technologies including Global Positioning System (GPS) and Radio Frequency Identification (RFID) have propelled the growth of a number of mobile services. Typically, these require maintaining the mobile objects' location and profile information and efficiently serving access requests on the past, present and future status of the moving objects. This creates inherent security and privacy challenges. One solution to this is to specify security policies to ensure controlled access. However, this significantly degrades system performance. To alleviate this, Atluri and Guo have proposed an unified index structure, STPR-tree, to organize both the moving objects and authorizations specified over them. A significant limitation of this approach is that it is unable to store past location information of objects and is therefore not capable of supporting security policies based on tracking of mobile users. In this paper, we propose a new unified index structure, called the SPPF-tree, which maintains past, present and future positions of the moving objects along with authorizations by employing partial persistent storage. Besides demonstrating how the SPPF-tree can be constructed and maintained, we provide algorithms to process queries where either the subject or the object or both are mobile. We provide a comprehensive experimental evaluation to establish the scalability and performance of our approach.
Keywords: Mobile data, indexing, spatiotemporal data, access control
