Location-Aware Query Processing and Optimization

Mohamed F. Mokbel (University of Minnesota) and Walid G. Aref (Purdue University)

The wide spread use of cellular phones, handheld devices, and GPS-like technology enables location-aware environments where virtually all objects are aware of their locations. Location-aware environments are characterized by the large numbers of moving objects and moving queries (also known as spatio-temporal queries). Such environments call for new query processing techniques that deal with the continuous movement and frequent updates of both spatio-temporal objects and queries. The goal of this tutorial is to: (1) Give an in-depth view on supporting location-aware queries as an increasingly interesting area of research, (2) Present the state-of-the-art techniques for efficient handling of location-aware snapshot queries and location-aware continuous queries, (3) Motivate the need for integrating location-awareness as a new query processing and optimization dimension, and (4) Raise several research challenges that need to be addressed towards a true support for location-aware queries in database management systems.

Mohamed F. Mokbel

Mohamed F. Mokbel (Ph.D., Purdue University, 2005) is an assistant professor in the Department of Computer Science and Engineering, University of Minnesota. His main research interests focus on advancing the

state of the art in the design and implementation of database engines to cope with the requirements of emerging applications (e.g., location-aware applications and sensor networks). Recently, he has led the efforts in incorporating location privacy in location-based applications. Dr. Mokbel is also interested in indexing, adaptive query processors, object-based storage devices, and geographic information systems. He is an ACM and IEEE member. For more information, please visit http://www.cs.umn.edu/~mokbel.

Walid G. Aref

Walid G. Aref is a professor of computer science at Purdue. His research interests are in extending the functionality of database systems in support of emerging applications, e.g., spatial, spatio-temporal, multimedia, biological, and sensor databases. He is also interested in indexing, data mining, and geographic information systems (GIS). Professor Aref's research has been supported by the National Science Foundation, the National Institute of Health, Purdue Research Foundation, CERIAS, Panasonic, and Microsoft Corp. In 2001, he received the CAREER Award from the National Science Foundation and in 2004, he received a Purdue University Faculty Scholar award. Professor Aref is a member of Purdue's Discovery Park Bindley Bioscience and Cyber Centers. He is on the editorial board of the VLDB Journal, a senior member of the IEEE, and a member of the ACM.

Location-Aware
Wireless Sensor Networks

Wang-Chien Lee and Yingqi Xu

A key aspect that makes wireless sensor networks different from traditional networks are their strong links to the physical world. By leveraging and processing raw information collected from numerous sensing devices, sensor networks are able to detect and monitor the actual physical phenomena happening at geographical locations/regions where sensing devices are deployed. In wireless sensor networks, users usually are concerned about physical phenomena associated with geographical location(s)/regions, rather than raw readings on some specific sensor nodes. For instance, a user is more likely to issue a request such as "tell me the average temperature in room 336, IST building" instead of "tell me the temperature readings at sensor node 1, 3, 10, and 17". Due to the importance of geographical location information to sensor networks and applications, sensor nodes equipped with GPS signal receiver are now available. Additionally, many localization schemes have been proposed such that sensor nodes are able to acquire their geographical locations even without GPS. These recent developments have made location-aware sensor networks feasible. The location-awareness of sensor nodes is essential for sensor readings to be meaningful for sensor network applications. This requires network functionalities designed with an emphasis on spatial/locational aspects.

There are many studies in the literature addressing various issues concerning network services of wireless sensor networks. However, these existing studies were mostly targeted at general network services in wireless sensor networks and thus failed to explore their spatial property. The spatial property of data, queries, and network dynamics open up new research issues. The purpose of this tutorial is to introduce

research issues and state-of-the-art solutions in the development of location-aware wireless sensor networks. We pay special attention to the aspects of data management and spatial network services.

Wang-Chien Lee

Wang-Chien Lee is an Associate Professor of Computer Science and Engineering in Pennsylvania State University. Dr. Lee performs cross-area research in database systems, pervasive/mobile computing, and networking. He is one of the few pioneers working on mobile data management and is the co-founder of the International Conference on Mobile Data Management. He has published over 100 technical papers in very selective conferences and journals. Dr. Lee is very active in various academic and industrial activities. He has taught several tutorials in top database and mobile computing conferences (e.g., ICDE, MOBICOM and MDM). He has served as a guest editor for several journal special issues (e.g., IEEE Transactions on Computers) and as a program committee co-chair for several international conferences and workshops. In addition, he has contributed to standardization activities in OMG technical meetings. Dr. Lee is a member of IEEE and ACM.

Yingqi Xu

Yingqi Xu (PhD., Pennsylvania State University, 2006) recently joined the Security Technology Group, CISCO Systems, Inc. Dr. Xu, as one of the pioneers working on location-aware sensor networks, has published many papers on wireless sensor networks in premier conferences and journals in networking, pervasive computing and databases. Her research interests include networking and data management issues in wireless sensor networks. Dr. Xu is a member of IEEE.

Privacy in Location-Based Services: State-of-the-Art and Research Directions

Mohamed F. Mokbel (University of Minnesota)

The explosive growth of location-detection devices (e.g., GPS-like devices and handheld devices) along with wireless communications and mobile databases results in realizing location-based applications that deliver specific information to their users based on their current locations. Examples of such applications include location-based store finder, location-based traffic reports, and location-based advertisements. Although location-based services promise safety and convenience, they threaten the privacy and security of users as such services explicitly require users to share private location information with the service and possibly with others. If a user wants to keep her location information private, she has to turn off her location-aware device and temporarily unsubscribe from the service. Unfortunately, recent studies show that such privacy concerns -- ranging from worries over employers snooping on their workers' whereabouts to fears of tracking by potential stalkers -- are a serious obstacle to wider adoption of location-based services. This tutorial aims to provide practitioners, researchers, and graduate students with the state of the art and major research issues in the important and practical research area of location privacy. The tutorial is divided into five main parts. The first part is concerned about legislatives issues and userperception of location privacy. In the

second part, we provide a comprehensive survey of the state-of-the-art system architectures and techniques in protecting location information in mobile environments. The third part overviews several techniques that an adversary can use to reveal the location privacy information along with a brief overview of how to avoid such privacy attacks. In the fourth part, we introduce the newly developing research area of privacy-aware query processors that enable users to: (a) obtain location-based services without sacrificing their privacy and (b) query private location data of others. Finally, the tutorial is concluded and summarized by showing how various components can be glued together to enable full-fledge privacy-aware location-based environments.

Mohamed F. Mokbel

Mohamed F. Mokbel (Ph.D., Purdue University, 2005) is an assistant professor in the Department of Computer Science and Engineering, University of Minnesota. His main research interests focus on advancing the state of the art in the design and implementation of database engines to cope with the requirements of emerging applications (e.g., location-aware applications and sensor networks). Recently, he has led the efforts in incorporating location privacy in location-based applications. Dr. Mokbel is also interested in indexing, adaptive query processors, object-based storage devices, and geographic information systems. He is an ACM and IEEE member. For more information, please visit http://www.cs.umn.edu/~mokbel.