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Dr. Wang-Chien Lee is a non-traditional database researcher.

Dr. Lee performs cross-area research in database systems, pervasive/mobile computing, and networking. He is particularly interested in developing data management techniques (including accessing, indexing, caching, aggregation, dissemination, and query processing) for supporting complex queries in a wide spectrum of networking and mobile environments such as peer-to-peer networks, mobile ad-hoc networks, wireless sensor networks, and wireless broadcast systems. Meanwhile, he works on object-oriented databases, XML, security, and information integration and retrieval. He has published over 80 technical papers, many in leading conferences and journals, including ACM Mobicom, ACM MobiSys, ACM SIGIR, VLDB, IEEE ICDE, IEEE ICDCS, IEEE ICNP, IEEE PerCom, IEEE INFOCOM, IEEE HPDC, IEEE TKDE, IEEE TPDS, IEEE TMC, IEEE TDSC, and VLDB Journal.

Mobile and Pervasive Data Access

Efficient data access for mobile and pervasive computing is a field of increasing importance for a wide range of mobile businesses and applications. It will be a key technology as ubiquitous wireless connectivity becomes a reality. Dr. Lee is one of the first few pioneers who started research in this area. He has been studying several fundamental issues in data and resource management of mobile computing systems, including: indexing and caching for reducing power consumption and increasing data access efficiency, data allocation for multiple wireless communication channels, cache invalidation and replacement policy for wireless data dissemination, and performance modeling and evaluation for wireless data access. Research result has been published in prestigious conferences and journals in the field, such as ACM MobiSys, ACM MobiCom, IEEE ICDE, IEEE ICDCS, IEEE HPDC, IEEE TKDE, ACM Wireless Network Journal, and ACM Mobile Networks and Applications Journal.

Selected Publication (Complete list)

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J. Xu, W.-C. Lee and X. Tang “Exponential Index: A Parameterized Distributed Indexing Scheme for Data on Air”, the Second International Conference on Mobile Systems, Applications, and Services (Mobisys'04), Boston, MA, June 6-9, 2004, pp. 153-164. [pdf]

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J. Xu, Q. Hu, W.-C. Lee and D.L. Lee “Performance Evaluation of an Optimal Cache Replacement Policy for Wireless Data Dissemination under Cache Consistency”, IEEE Transaction on Knowledge and Data Engineering (TKDE), Volume 16, No. 1, January, 2004, pp. 125-139. [pdf]

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Q. Hu, D.L. Lee, and W.-C. Lee, “Power Conservative Multi-Attribute Queries on Data Broadcast”, IEEE International Conference on Data Engineering (ICDE'00), San Diego. Feb. 2000, pp. 157-166. [pdf]

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W.-C. Lee, Q. Hu, D.L. Lee, “A Study of Channel Allocation Methods for Data Dissemination in Mobile Computing Environments” (with Q. Hu and D.L. Lee), ACM Mobile Networks and Applications Journal (MONET): Special Issue on Resource Management in Wireless Network, Volume 4, No. 2, 1999, pp. 117-129. [pdf]

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Q. Hu, D.L. Lee, and W.-C. Lee, “Performance Evaluation of a Wireless Hierarchical Data Dissemination System”, ACM/IEEE International Conference on Mobile Computing and Networking (Mobicom'99), Seattle, Washington, August 1999, pp. 163-173. [pdf]

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W.-C. Lee and D.L. Lee, “Signature Caching Techniques for Information Filtering in Mobile Environments”, ACM Wireless Networks Journal (WINET), Vol. 5, No. 1, January 1999, pp. 57-67. [pdf]

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W.-C. Lee and D.L. Lee, “Using Signature Techniques for Information Filtering in Wireless and Mobile Environments”, Distributed and Parallel Databases: Special Issue on Database and Mobile Computing, Vol. 4, No. 3, July 1996, pp. 205-227. [pdf]

 

Location-Based Services

Location-based services (LBSs) have emerged as one of the killer applications for mobile computing and wireless data services. These LBSs are critical to public safety, transportation, emergency response, and disaster management, while providing great market values to companies and industries. Efficient processing of location-based spatial queries (LBSQs), which refer to a set of spatial queries that retrieve information based on the current locations of mobile users, is crucial to the provision of LBSs. Due to the unrestricted mobility of users in the pervasive computing environments, the LBSQs are distinct from the traditional spatial queries. For example, a traveler may issue a query "find me the three nearest restaurants". The answer to this query is dependent on the location where the traveler receives the query result. Dr. Lee has been investigating new ways of indexing and caching spatial data to support the processing of LBSQs including point query, planar point query, window query, nearest neighbor (NN) search, k nearest neighbor (KNN) search, continuous nearest neighbor (CNN) search, spatial join, and other complex spatial queries. He has also been working on a new query type, called Nearest Surrounder Queries (NSQ). In addition to the traditional point-to-point communication channels, he is particularly interested in wireless data broadcast channels, which can serve a large number of mobile users simultaneously and thus naturally scale up the services to meet heavy demands. Fundamental issues faced by all the spatial indexes and caching schemes (such as large index search space, large index size, linear streaming property of wireless data broadcast, continuous movement and requests of mobile users, and cache replacement/invalidation) have been tackled. Query processing algorithms and new mobile caching mechanisms have been developed in support of various spatial queries for mobile users. Research in this direction is supported in part by an NSF grant. The result is expected to have significant impacts on advancing the fields of spatial databases and pervasive computing. An overview of the research challenges and issues in this topic has been published in the IEEE Pervasive Computing Magazine and also presented as a tutorial in IEEE ICDE’04. In addition, some recently research results in this direction have been published in prestigious journals and conferences, such as VLDB Journal, IEEE TKDE, IEEE ICDCS, IEEE ICDE, and IEEE PerCom.

Selected Publication (Complete list)

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C.K. Lee, W.-C. Lee, B. Zheng, and J. Xu, "Caching Complementary Space for Location-Based Services", International Conference on Extending Database Technology (EDBT'06), Munich, Germany, March 2006, pp. 1020-1038.  [pdf]

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C.K. Lee, W.-C. Lee, and H.V. Leung, “Nearest Surrounder Search”, IEEE International Conference on Data Engineering (ICDE’06), Atlanta, GA, April 2006, 10 pages. [pdf]

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B. Zheng, J. Xu, W,-C. Lee, D.L. Lee, “Grid-Partition Index: A Hybrid Method for Nearest-Neighbor Queries in Wireless Location-Based Services”, Very Large Data Base Journal (VLDBJ), Volume 15, No. 1, January 2006, pp. 21-39. [pdf]

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W.-C. Lee and B. Zheng, “DSI: A Fully Distributed Spatial Index for Location-Based Wireless Broadcast Services”, IEEE International Conference on Distributed Computing Systems (ICDCS’05), Columbus, OH, June, 2005, pp. 349-358. [pdf]

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H. Hu, J. Xu, W.S. Wong, B. Zheng, D.L. Lee, and W.-C. Lee, “Proactive Caching for Spatial Queries in Mobile Environments”, IEEE International Conference on Data Engineering (ICDE’05), Tokyo, April, 2005, pp. 403-414. [pdf]

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B. Zheng, J. Xu, W,-C. Lee, D.L. Lee, “The D-tree: An Index Structure for Planar Point Queries in Location-Based Wireless Services”, IEEE Transaction on Knowledge and Data Engineering (TKDE), Volume 16, No. 12, December, 2004, pp. 1526-1542. [pdf]

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B. Zheng, W.-C. Lee, and D.L. Lee, “Spatial Index on Air”, IEEE International Conference on Pervasive Computing and Communications (PerCom’03), Dallas-Fort Worth, Texas, March 23-26, 2003 pp. 297-304. [pdf]

 

Peer-to-Peer (P2P) Computing

Peer-to-peer (P2P) computing has received a lot of attention due to the popularity of applications such as SETI, Napster, Gnutella, Morpheus and BitTorrent. The goal of Dr. Lee’s research in this area is to build data management systems in support of complex queries and applications on P2P networks. He has been working on developing overlay network infrastructures and search algorithms for those queries. Since an efficient search mechanism is a key determinant to the scalability of P2P systems that can hold a massive amount of data, he started the research by attacking research issues related to the P2P search problem. A new indexing mechanism, called neighborhood signatures, has been proposed for focusing P2P searches along selective network paths instead of trying arbitrary paths blindly. This technique trades a small amount of storage overhead for significant reduction of overall network traffic. In addition, recognizing the need for using semantic information in P2P search, a novel overlay network infrastructure, called semantic small world (SSW), has been developed for P2P systems. The idea is to organize peers with semantically similar data closer to each other into clusters and to form a small world overlay network in the process. SSW is shown to be much more scalable to very large network sizes and very large numbers of data objects compared other state-of-the-art semantic-based search technique for P2P systems. In addition, SSW is adaptive to distribution of data and locality of interest; is very resilient to failures; and has excellent load balancing property. More recently, Dr. Lee has developed an efficient and scalable P2P system based on a new technique, called Networked R-Tree (NR-Trees). NR-trees facilitate the processing of complex multi-dimensional queries (including both range and KNN queries) in P2P networks. Research in this direction is supported in part by an NSF grant. Research result in this direction has been published in prestigious conferences such as IEEE ICNP and IEEE ICDCS.

Selected Publication (Complete list)

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DPTree: A Balanced Tree Based Indexing Framework For Peer-To-Peer Systems (with M. Li and A. Sivasubramaniam), IEEE International Conference on Network Protocols (ICNP'06), Santa Barbara, CA, November 2006, pp. 12-21.

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PENS: an Algorithm for Density-Based Clustering in Peer-to-Peer Systems (with M. Li, G. Lee, and A. Sivasubramaniam), International Conference on Scalable Information Systems (INFOSCALE’06), Hong Kong, May 2006, 8 pages [pdf].

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B. Liu, W.-C. Lee, and D.L. Lee, “Supporting Complex Multi-dimensional Queries in P2P Systems”, IEEE International Conference on Distributed Computing Systems (ICDCS’05), Columbus, OH, June, 2005, pp. 155-164. [pdf]

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M. Li, W.-C. Lee, and A. Sivasubramaniam, “Semantic Small World: An Overlay Network for Peer-to-Peer Search”, IEEE International Conference on Network Protocols (ICNP’04), Berlin, Germany, October, 2004, pp. 228-238. [pdf]

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M. Li, W.-C. Lee, and A. Sivasubramaniam, “Neighborhood Signatures for Searching P2P Networks”, International Database Engineering and Application Symposium (IDEAS’03), Hong Kong, July 16- 18, 2003, pp. 142-151. [pdf]

 

Wireless Sensor Networks

Wireless sensor networks have recently received a lot of attention due to a wide range of applications such as object tracking, environmental monitoring, warehouse inventory, and health care. In these applications, physical data is continuously collected by the sensor nodes in order to facilitate application specific processing and analysis. The goal of Dr. Lee’s research in this area is to build data management systems for wireless sensor networks in support of data collection, aggregation, dissemination, in-network query processing and query optimization. Dr. Lee is particularly interested in location-aware wireless sensor networks since sensor network applications typically are concerned more about physical phenomena or events associated with a geographical location or region than the raw data on a specific sensor node. His research effort is focused on: 1) location tracking of moving objects; 2) location-based routing; 3) complex query processing (including window, KNN, and aggregation queries). Two prediction-based energy saving methods (called PES and DPR) are developed to reduce energy consumption of the sensor nodes in object tracking sensor networks during monitoring and reporting activities, correspondingly. PES predicts the future movement of the tracked objects to provide the basis for a wake up mechanism to decide which sensor nodes need to be activated for object monitoring. DPR reduces the number of reporting messages (and thus energy) by predicting the moves of the monitored objects in both of the base station and sensor nodes. In addition, by observing that many sensor applications for object tracking can tolerate a certain degree of imprecision in the location data of the tracked objects, an innovative technique (called EASE) was developed to efficiently answer approximate location queries by keeping error-bounded imprecise location data at some designated storage nodes in an object tracking sensor network. The result shows that EASE significantly cuts now network traffic and prolongs the network lifetime. Next, a novel stateless spatial routing protocol, called PSGR, for location-aware sensor networks was developed. Based on PSGR, sensor nodes can locally determine their priority to serve as the next relay node using dynamically estimated network density and effectively suppress potential communication collisions without prolonging routing delays. PSGR also overcomes the communication void problem using two alternative stateless schemes, rebroadcast and bypass. Research result shows that PSGR exhibits superior performance in terms of energy consumption, routing latency and delivery rate. Moreover, based on location-based routing, an infrastructure-free window query processing technique for wireless sensor networks, called itinerary based window query execution (IWQE), has also been developed. IWQE combines query propagation and data aggregation into one single stage for execution along a well-designed itinerary inside a query window. Furthermore, two alternative algorithms, namely the GeoRouting Tree (GRT) and the KNN Boundary Tree (KBT) have been proposed for in-network processing of KNN queries. The former is based on a distributed spatial index structure and the latter is based upon ad-hoc spatial routing. This is the first study on KNN query processing in wireless sensor networks. Research result in this direction has been published in selective conferences such as IEEE ICDE, IEEE MASS and IEEE SECON. Research in this direction is supported in part by an NSF grant.

Selected Publication (Complete list)

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Y. Xu, W.-C. Lee, and Jianliang Xu, "Analysis of a Loss-Resilient Proactive Data Transmission Protocol in Wireless Sensor Networks", IEEE Conference on Computer Communications (Infocom'07), Anchorage, Alaska, USA, May 2007, to appear.

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Y. Xu and W.-C. Lee, "Exploring Spatial Correlation for Link Quality Estimation in Wireless Sensor Networks", IEEE International Conference on Pervasive Computing and Communications (PerCom’06), Pisa, Italy, March 2006, pp. 200-211.  [pdf]

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C.K. Lee, W.-C. Lee, B. Zheng, and J. Winter, "Processing Multiple Aggregation Queries in Geo-Sensor Networks", the Eleventh International Conference on Database Systems for Advanced Applications (DASFAA'06), Singapore, April 2006, pp. 20-34.  [pdf]

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Y. Xu, W.-C. Lee, J. Xu, and G. Mitchell, "Processing Window Queries in Wireless Sensor Networks", IEEE International Conference on Data Engineering (ICDE’06), Atlanta, GA, April 2006, 10 pages. [pdf]

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Y. Xu, W.-C. Lee, J. Xu, and G. Mitchell, “PSGR: Priority-based Stateless Geo-Routing in Wireless Sensor Networks The Second IEEE International Conference on Mobile Ad-hoc and Sensor Systems (MASS'05), Washington D.C., November, 2005, 8 pages. [pdf]

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J. Xu, X. Tang and W.-C. Lee, “EASE: An Energy-Efficient In-Network Storage Scheme for Object Tracking in Sensor Networks”, IEEE International Conference on Sensor and Ad Hoc Communications and Networks (SECON'05), Santa Clara, California, September 2005. [pdf]

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J. Winter, Y. Xu and W.-C. Lee, “Energy Efficient Processing of K Nearest Neighbor Queries in Location-aware Sensor Networks”, the Second International Conference on Mobile and Ubiquitous Systems: Networking and Services (Mobiquitous'05), San Diego, CA, July, 2005, pp. 281-292. [pdf]

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Y. Xu, J. Winter and W.-C. Lee, “Dual Prediction-based Reporting Mechanism for Object Tracking Sensor Networks”, the First International Conference on Mobile and Ubiquitous Systems: Networking and Services (Mobiquitous'04), Boston, MA, August 22-26, 2004, pp. 154-163. [pdf]

 

Time-Critical and Secure Wireless Data Broadcast

Wireless data broadcast services have been commercially available (e.g., StarBand, Hughes Network, and MSN Direct) for many years. Recently, there is a push for such services and systems from the industry and various standard bodies. For example, the Third Generation Partnership Project 2 (http://www.3gpp2.org/) is developing Broadcast and Multicast Service in cdma2000 Wireless IP network. While most of the existing work focused on system issues, there is a need for these wireless data broadcast systems to support various application requirements such as timeliness and security. Dr. Lee’s research in this area studies on-line scheduling algorithms, secure air indexing techniques, and key management schemes for wireless data broadcast services. A novel broadcast scheduling algorithm (called SIN-α) that takes the urgency of requests and the number of outstanding requests into account has been developed. The theoretical bound of request drop rate when the request arrival rate rises towards infinity is derived. In addition, he has investigated the tradeoff between performance and confidentiality of signature-based air indexes in terms of their relationships to false drop and false guess probabilities of the signatures. This is the first time the issue of confidentiality loss in air indexing has been identified and discussed in the literature. Finally, an efficient key management scheme, KTR, has been developed to let multiple broadcast programs share a single key tree such that the users subscribing these programs need to hold only a small number of keys. In this scheme, rekey cost is minimized by identifying the minimum set of keys that must be changed to ensure broadcast security. This is also the first time a key management scheme being proposed for wireless data broadcast. Research result in this area has been published in journals and conferences such as IEEE TPDS, ACM CIKM, and ACM Mobiquitous.

Selected Publication (Complete list)

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Q. Gu, P. Liu, C.-H. Chu and W.-C. Lee, KTR: an Efficient Key Management Scheme For Secure Data Access Control in Wireless Broadcast Services, IEEE Transactions on Dependable and Secure Computing (TDSC), to appear.

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J. Xu, X. Tang, and W.-C. Lee, “On Scheduling Time-Critical On-Demand Broadcast”, IEEE Transaction on Distributed and Parallel Systems, Volume 17, Issue 1, Jan. 2006, pp. 3-14. [pdf]

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Q. Tan, W.-C. Lee, B. Zheng, P. Liu, and D. Lee, “Balancing Performance and Confidentiality in Air Index”, ACM Fourteenth Conference on Information and Knowledge Management (CIKM'05), Breman, Germany, October 2005, to appear. [pdf]

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Q. Gu, P. Liu, W.-C. Lee and C.-H. Chu, “KTR: an Efficient Key Management Scheme for Air Access Control”, the Second International Conference on Mobile and Ubiquitous Systems: Networking and Services (Mobiquitous'05), San Diego, CA, July, 2005, pp. 499-501. (Poster paper) [pdf]

 

Information Retrieval, Visualization, and Analysis

The proliferation of Web-based information services, heterogeneous information content and resources, and ubiquitous Internet access have brought great challenges to integration and search of information. Dr. Lee is developing architectures, algorithms and tools that facilitate efficient retrieval, integration, search, analysis, mining, and visualization of information from disparate and large information sources. He is particularly interested Information related to, while not limited to, space and time. Research in this direction is supported in part by a grant from ARDA (the advanced research and development activities) which is a joint Department of Defense/Intelligence Community organization. He is also involved in re-architecting and implementing the next generation CiteSeer (http://citeseer.ist.psu.edu/) in order to tackle the scalability and other critical performance and research issues. One primary design goal of this new architecture is to provide more flexible and versatile web services for specialized information search and system integration on the Internet. Finally, the Internet information services will eventually be mobilized and personalized such that the users may access to information without geographical limits. He is looking into technologies for supporting various services, including multimedia (such as voice, data, text, video streaming) for mobile users.

 Selected Publication (Complete list)

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Y. Song, Z. Zhuang, H. Li, Q. Zhao, J. Li, W.-C. Lee, and L. Giles, Real-time Automatic Tag Recommendation (with ), International Conference on Research & Development on Information Retrieval  (SIGIR 2008), Singapore, July, 2008, to appear.

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H. Li, I. Councill, W.-C. Lee and L. Giles, CiteSeerX: an Architecture and Web Service Design for an Academic Document Search Engine,  the International World Wide Web Conference (WWW'06), Edinburgh, Scotland, May 23-26, 2006, pp. 187-188. [pdf] (Poster Paper)

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 I. Councill, H. Li, Z. Zhuang, S. Debnath, L. Bolelli, W.-C. Lee, A. Sivasubramaniam, L. Giles, Learning Metadata from the Evidence in an On-Line Citation Matching Scheme, ACM/IEEE Joint Conference on Digital Libraries (JCDL'06), Chapel Hill, NC, USA, June 11-15, 2006, pp. 276-285. (Vannevar Bush Best Paper Candidate). [pdf]

 

Mobile Ad Hoc Network

Dr. Lee has been investigating an Internet-based mobile ad hoc network (called IMANET) that facilitates mobile hosts to access information on the Internet via limited access points. An aggregate cache is built on the IMANET where the mobile hosts' local caches are integrated as a unified cache. Admission control and cache replacement policies for this aggregate cache have been developed. Research result in this direction has been published in conferences and journal such as IEEE MASS and Ad Hoc Networks Journal.

Selected Publication

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S. Lim, W.-C. Lee, G. Cao, and C. Das, “A Novel Caching Scheme for Improving Internet-based Mobile Ad Hoc Networks Performance”, Ad Hoc Networks Journal, Volume 4, Issue 2. 2006, pp. 225-239. [pdf]

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S. Lim, W.-C. Lee, G. Cao, and C. Das, “Performance Comparison of Cache Invalidation Strategies for Internet-based Mobile Ad Hoc Networks”, the First IEEE International Conference on Mobile Ad-hoc and Sensor Systems (MASS'04), Fort Lauderdale, Florida, USA, October 25-27, 2004, pp. 104-113. [pdf]

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S. Lim, W.-C. Lee, G. Cao, and C. Das, “A Novel Caching Scheme for Internet based Mobile Ad Hoc Networks”, International Conference on Computer Communications and Networks (ICCCN’03), Dallas, TX, Oct 2003, U.S.A, pp. 38-43. [pdf]

 

XML and Access Control

XML is emerging as a de facto format of the Internet era for information exchange and system integration. As the distribution and sharing of XML information over the World Wide Web become increasingly important, the needs for flexible and efficient storage, access control and query processing of XML data naturally arise. Dr. Lee’s research work contributes to this area in two aspects: 1) applying database technologies (such as metadata modeling and data warehouse) to integrate Web and Relational data; 2) developing practical solutions to the problems of XML data access control. He has developed a metadata driven approach to load XML data into a relational database. One novel part of this work is that the processes of relational schema generation and loading of XML data are all automatic. This technology is expected to make a significant impact on e-business and e-services. A prototype system based on this innovation was implemented and two patents have been filed. For XML access control, a new middleware technique, called QFilter, based on non-deterministic finite automata has been developed to enforce access control policies in an efficient and non-redundant fashion. QFilter filters out all or part of unauthorized requests by query rewriting technique before a XML engine responds to the rewritten queries. Research result in this area has been published in conferences such as ACM CIKM and IEEE RIDE.

Selected Publication (Complete list)

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Y.-H. Chang and C.T. Lee and W.-C. Lee, "Path Gluing: A New Technique for Efficient XML Query Processing", Journal of Information Science and Engineering (JISE), to appear.

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B. Luo, D.W. Lee, W.-C. Lee, and P. Liu, “QFilter: Fine-Grained Run-Time XML Access Control via NFA-based Query Rewriting”, ACM International Conference on Information and Knowledge Management (CIKM’04), Washington D.C., Nov. 8-13, 2004, pp. 543-552. [pdf]

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D.W. Lee, W.-C. Lee, and P. Liu, “Supporting XML Security Models using Relational Databases: A Vision”, the First XML Database Symposium (XSym'03), Berlin, Germany, Sept. 8, 2003, pp. 267-281. [pdf]

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X. Zhang, W.-C. Lee, G. Mitchell, and E. Rundensteiner “Clock: Synchronizing Internal Relational Storage with External XML Documents”, the Eleventh International Workshop on Research Issues in Data Engineering: Document Management, Heidelberg, Germany, 2001, pp. 111-118. [pdf]

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W.-C. Lee, G. Mitchell and X. Zhang, “Integrating XML Data with Relational Databases”, IEEE International Workshop on Knowledge Discovery and Data Mining in World Wide Web, Taipei, Taiwan, April 10-13, 2000, pp. F47-F53. [pdf]

 

Object-Oriented Database

Database is one of the most vitally important areas for enterprise and web applications. Dr. Lee has worked on indexing techniques for nested query processing in object-oriented database systems (OODBSs) since the early stage of his research career. He has proposed two signature file schemes and two classes of path-dictionary-based indexing organizations for nested query processing. These indexing techniques significantly improve the efficiency of retrieval and update operations in OODBSs with a small storage overhead. Moreover, they can be applied not only to OODBSs but also Relational, Object-Relational Database Systems, and now XML-based Data Repositories. Research result has been published in very selective journal and conferences in the field, such as IEEE TKDE and ACM CIKM.

Selected Publication (Complete list)

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W.-C. Lee and D.L. Lee, “Path Dictionary: A New Approach to Query Processing in Object-Oriented Database”, IEEE Transaction on Knowledge and Data Engineering (TKDE), Volume 10, No. 3, May/June 1998, pp. 371-388. [pdf]

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W.-C. Lee and D.L. Lee, “Combining Indexing Technique with Path Dictionary for Nested Object Queries”, the Fourth International Conference on Database Systems for Advanced Applications (DASFAA'95), Singapore, Apr. 1995, pp. 107-114. [pdf]

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W.-C. Lee and D.L. Lee, “Using Path Information for Query Processing in Object-Oriented Database Systems”, ACM International Conference on Information and Knowledge Management (CIKM'94), Gathersberg, MD, Nov. 1994, pp. 64-71. [pdf]