Oktie Hassanzadeh 
contact information
Research Scientist (RSM)IBM Research AI, Thomas J. Watson Research Center, Yorktown Heights, NY, USA
links
Professional Associations
Professional Associations: ACM | ACM SIGIR | ACM SIGMOD | IEEE Computer Society | IEEE Member | W3C - World Wide Web Consortium2018
Inducing Implicit Relations from Text using Distantly Supervised Deep Nets
Michael Glass, Alfio Gliozzo, Oktie Hassanzadeh, Nandana Mihindukulasooriya, Gaetano Rossiello
ISWC (To Appear), 2018
Michael Glass, Alfio Gliozzo, Oktie Hassanzadeh, Nandana Mihindukulasooriya, Gaetano Rossiello
ISWC (To Appear), 2018
Semantic Concept Discovery Over Event Databases
Oktie Hassanzadeh, Shari Trewin and Alfio Gliozzo
The Semantic Web. ESWC 2018. Lecture Notes in Computer Science, pp. 288-303, Springer, Cham
Abstract (Winner of Best In Use Paper Award)
Oktie Hassanzadeh, Shari Trewin and Alfio Gliozzo
The Semantic Web. ESWC 2018. Lecture Notes in Computer Science, pp. 288-303, Springer, Cham
Abstract (Winner of Best In Use Paper Award)
2017
Semantic Concept Discovery Over Event Data
Oktie Hassanzadeh, Shari Trewin, Alfio Massimiliano Gliozzo
ISWC (Industry Track), 2017
Oktie Hassanzadeh, Shari Trewin, Alfio Massimiliano Gliozzo
ISWC (Industry Track), 2017
Socrates: Deep Relational Knowledge Induction (Semantic Web Challenge 2017 Winner)
Michael Glass, Nandana Mihindukulasooriya, Oktie Hassanzadeh, Alfio Gliozzo
ISWC, 2017
Michael Glass, Nandana Mihindukulasooriya, Oktie Hassanzadeh, Alfio Gliozzo
ISWC, 2017
Large-scale structural and textual similarity-based mining of knowledge graph to predict drug--drug interactions
Abdelaziz, Ibrahim and Fokoue, Achille and Hassanzadeh, Oktie and Zhang, Ping and Sadoghi, Mohammad
Web Semantics: Science, Services and Agents on the World Wide Web44, 104--117, Elsevier, 2017
Abdelaziz, Ibrahim and Fokoue, Achille and Hassanzadeh, Oktie and Zhang, Ping and Sadoghi, Mohammad
Web Semantics: Science, Services and Agents on the World Wide Web44, 104--117, Elsevier, 2017
OM-2017: Proceedings of the Twelfth International Workshop on Ontology Matching
Shvaiko, Pavel and Euzenat, J{\'e}r{\^o}me and Jim{\'e}nez-Ruiz, Ernesto and Cheatham, Michelle and Hassanzadeh, Oktie
OM 2017-12th International Workshop on Ontology Matching, pp. 1--233
Shvaiko, Pavel and Euzenat, J{\'e}r{\^o}me and Jim{\'e}nez-Ruiz, Ernesto and Cheatham, Michelle and Hassanzadeh, Oktie
OM 2017-12th International Workshop on Ontology Matching, pp. 1--233
Matching web tables with knowledge base entities: From entity lookups to entity embeddings
Efthymiou, Vasilis and Hassanzadeh, Oktie and Rodriguez-Muro, Mariano and Christophides, Vassilis
International Semantic Web Conference, pp. 260--277, 2017
Efthymiou, Vasilis and Hassanzadeh, Oktie and Rodriguez-Muro, Mariano and Christophides, Vassilis
International Semantic Web Conference, pp. 260--277, 2017
2016
Self-Curating Databases
Mohammad Sadoghi, Kavitha Srinivas, Oktie Hassanzadeh, Yuan-Chi Chang, Mustafa Canim, Achille Fokoue, and Yishai Feldman
EDBT 2016
Mohammad Sadoghi, Kavitha Srinivas, Oktie Hassanzadeh, Yuan-Chi Chang, Mustafa Canim, Achille Fokoue, and Yishai Feldman
EDBT 2016
Predicting drug-drug interactions through large-scale similarity-based link prediction
Achille Fokoue, Mohammad Sadoghi, Oktie Hassanzadeh, Ping Zhang
WWW, 2016
Achille Fokoue, Mohammad Sadoghi, Oktie Hassanzadeh, Ping Zhang
WWW, 2016
Proc. 10th ISWC workshop on ontology matching (OM)
Pavel Shvaiko, J{'e}r{^o}me Euzenat, Ernesto Jim{'e}nez-Ruiz, Michelle Cheatham, Oktie Hassanzadeh
Ruiz, M Cheatham… - 2016 - hal.archives-ouvertes.fr, No commercial editor.
Pavel Shvaiko, J{'e}r{^o}me Euzenat, Ernesto Jim{'e}nez-Ruiz, Michelle Cheatham, Oktie Hassanzadeh
Ruiz, M Cheatham… - 2016 - hal.archives-ouvertes.fr, No commercial editor.
Predicting Drug-Drug Interactions Through Similarity-Based Link Prediction Over Web Data
Achille Fokoue, Oktie Hassanzadeh, Mohammad Sadoghi, Ping Zhang
Proceedings of the 25th International Conference Companion on World Wide Web, pp. 175--178, 2016
Achille Fokoue, Oktie Hassanzadeh, Mohammad Sadoghi, Ping Zhang
Proceedings of the 25th International Conference Companion on World Wide Web, pp. 175--178, 2016
2015
Understanding a Large Corpus of Web Tables Through Matching with Knowledge Bases--An Empirical Study
Hassanzadeh, Oktie and Ward, Michael J and Rodriguez-Muro, Mariano and Srinivas, Kavitha
Ontology Matching, 25, 2015
Hassanzadeh, Oktie and Ward, Michael J and Rodriguez-Muro, Mariano and Srinivas, Kavitha
Ontology Matching, 25, 2015
Understanding a Large Corpus of Web Tables Through Matching with Knowledge Bases--An Empirical Study
Oktie Hassanzadeh, Michael J Ward, Mariano Rodriguez-Muro, Kavitha Srinivas
OM 2015
Oktie Hassanzadeh, Michael J Ward, Mariano Rodriguez-Muro, Kavitha Srinivas
OM 2015
LinkedCT Live: Platform for Online Curation of Clinical Trials Data"
Oktie Hassanzadeh, Ren{'e}e J Miller, Fatemeh Nargesian, Erkang Zhu
ISWC 2015
Oktie Hassanzadeh, Ren{'e}e J Miller, Fatemeh Nargesian, Erkang Zhu
ISWC 2015
Toward a complete dataset of drug--drug interaction information from publicly available sources
Serkan Ayvaz, John Horn, Oktie Hassanzadeh, Qian Zhu, Johann Stan, Nicholas P Tatonetti, Santiago Vilar, Mathias Brochhausen, Matthias Samwald, Majid Rastegar-Mojarad, others
Journal of biomedical informatics55, 206--217, Elsevier, 2015
Serkan Ayvaz, John Horn, Oktie Hassanzadeh, Qian Zhu, Johann Stan, Nicholas P Tatonetti, Santiago Vilar, Mathias Brochhausen, Matthias Samwald, Majid Rastegar-Mojarad, others
Journal of biomedical informatics55, 206--217, Elsevier, 2015
Understanding a Large Corpus of Web Tables Through Matching with Knowledge Bases – An Empirical Study
Oktie Hassanzadeh, Michael J. Ward, Mariano Rodriguez-Muro, Kavitha Srinivas
Proceedings of the Tenth International Workshop on Ontology Matching (OM-2012), 2015
Oktie Hassanzadeh, Michael J. Ward, Mariano Rodriguez-Muro, Kavitha Srinivas
Proceedings of the Tenth International Workshop on Ontology Matching (OM-2012), 2015
LinkedCT Live: Platform for Online Curation of Clinical Trials Data
Oktie Hassanzadeh, Renee J Miller, Fatemeh Nargesian, Erkang Zhu
The Semantic Web - ISWC 2015 - 14th International Semantic Web Conference (System Demonstration)
Oktie Hassanzadeh, Renee J Miller, Fatemeh Nargesian, Erkang Zhu
The Semantic Web - ISWC 2015 - 14th International Semantic Web Conference (System Demonstration)
Automatic Curation of Clinical Trials Data in LinkedCT
Oktie Hassanzadeh, Renee J. Miller
The Semantic Web - ISWC 2015 - 14th International Semantic Web Conference, October 11-15, 2015, Proceedings, pp. 270--278
Oktie Hassanzadeh, Renee J. Miller
The Semantic Web - ISWC 2015 - 14th International Semantic Web Conference, October 11-15, 2015, Proceedings, pp. 270--278
VizCurator: A Visual Tool for Curating Open Data
Bahar Ghadiri Bashardoost, Christina Christodoulakis, Soheil Hassas Yeganeh, Ren\'{e}e J. Miller, Kelly Lyons, Oktie Hassanzadeh
Proceedings of the 24th International Conference on World Wide Web Companion, WWW 2015, Florence, Italy, May 18-22, 2015 - Companion Volume, pp. 195--198
Bahar Ghadiri Bashardoost, Christina Christodoulakis, Soheil Hassas Yeganeh, Ren\'{e}e J. Miller, Kelly Lyons, Oktie Hassanzadeh
Proceedings of the 24th International Conference on World Wide Web Companion, WWW 2015, Florence, Italy, May 18-22, 2015 - Companion Volume, pp. 195--198
Schema Management for Document Stores
Lanjun Wang, Oktie Hassanzadeh, Shuo Zhang, Juwei Shi
PVLDB 8(9), 922--933, 2015
Lanjun Wang, Oktie Hassanzadeh, Shuo Zhang, Juwei Shi
PVLDB 8(9), 922--933, 2015
2014
Exploring Big Data with Helix: Finding Needles in a Big Haystack
Jason B. Ellis, Achille Fokoue, Oktie Hassanzadeh, Anastasios Kementsietsidis, Kavitha Srinivas, Michael J. Ward
SIGMOD Record 43(4), 43--54, 2014
Jason B. Ellis, Achille Fokoue, Oktie Hassanzadeh, Anastasios Kementsietsidis, Kavitha Srinivas, Michael J. Ward
SIGMOD Record 43(4), 43--54, 2014
2013
An evaluation of clustering algorithms in duplicate detection
Bilal Hussain, Oktie Hassanzadeh, Fei Chiang, Hyun Chul Lee, Ren{'e}e J Miller
Technical Report, Technical Report CSRG-620, University of Toronto, Department of Computer Science, 2013
Bilal Hussain, Oktie Hassanzadeh, Fei Chiang, Hyun Chul Lee, Ren{'e}e J Miller
Technical Report, Technical Report CSRG-620, University of Toronto, Department of Computer Science, 2013
Collective ontology alignment
Jason B Ellis, Oktie Hassanzadeh, Kavitha Srinivas, Michael J Ward
Proceedings of the 8th International Conference on Ontology Matching-Volume 1111, pp. 219--220, 2013
Jason B Ellis, Oktie Hassanzadeh, Kavitha Srinivas, Michael J Ward
Proceedings of the 8th International Conference on Ontology Matching-Volume 1111, pp. 219--220, 2013
Extending the “Web of Drug Identity” with knowledge extracted from United States product labels
Oktie Hassanzadeh, Qian Zhu, Robert Freimuth, Richard Boyce
AMIA Summits on Translational Science Proceedings2013, 64, American Medical Informatics Association
Oktie Hassanzadeh, Qian Zhu, Robert Freimuth, Richard Boyce
AMIA Summits on Translational Science Proceedings2013, 64, American Medical Informatics Association
Next generation data analytics at IBM research
Oktie Hassanzadeh, Anastasios Kementsietsidis, Benny Kimelfeld, Rajasekar Krishnamurthy, Fatma {"O}zcan, P, Ippokratis is
Proceedings of the VLDB Endowment 6(11), 1174--1175, VLDB Endowment, 2013
Oktie Hassanzadeh, Anastasios Kementsietsidis, Benny Kimelfeld, Rajasekar Krishnamurthy, Fatma {"O}zcan, P, Ippokratis is
Proceedings of the VLDB Endowment 6(11), 1174--1175, VLDB Endowment, 2013
Dynamic enhancement of drug product labels to support drug safety, efficacy, and effectiveness.
Richard D Boyce, John R Horn, Oktie Hassanzadeh, Anita de Waard, Jodi Schneider, Joanne S Luciano, Majid Rastegar-Mojarad, Maria Liakata
J. Biomedical Semantics4, 5, 2013
Richard D Boyce, John R Horn, Oktie Hassanzadeh, Anita de Waard, Jodi Schneider, Joanne S Luciano, Majid Rastegar-Mojarad, Maria Liakata
J. Biomedical Semantics4, 5, 2013
Collective ontology alignment.
Jason B Ellis, Oktie Hassanzadeh, Kavitha Srinivas, Michael J Ward
OM, pp. 219--220, 2013
Jason B Ellis, Oktie Hassanzadeh, Kavitha Srinivas, Michael J Ward
OM, pp. 219--220, 2013
Discovering linkage points over web data
Oktie Hassanzadeh, Ken Q Pu, Soheil Hassas Yeganeh, Ren\'ee J Miller, Lucian Popa, Mauricio A Hern\'andez, Howard Ho
Proceedings of the VLDB Endowment 6(6), 445--456, VLDB Endowment, 2013
Oktie Hassanzadeh, Ken Q Pu, Soheil Hassas Yeganeh, Ren\'ee J Miller, Lucian Popa, Mauricio A Hern\'andez, Howard Ho
Proceedings of the VLDB Endowment 6(6), 445--456, VLDB Endowment, 2013
Extending the "Web of Drug Identity" with Knowledge Extracted from United States Product Labels
Oktie Hassanzadeh, Qian Zhu, Robert R. Freimuth, Richard D. Boyce
Proceedings of the 2013 AMIA Summit on Translational Bioinformatics
Oktie Hassanzadeh, Qian Zhu, Robert R. Freimuth, Richard D. Boyce
Proceedings of the 2013 AMIA Summit on Translational Bioinformatics
Dynamic enhancement of drug product labels to support drug safety, efficacy, and effectiveness
R.D. Boyce, J.R. Horn, O. Hassanzadeh, A. de Waard, J. Schneider, J.S. Luciano, M. Rastegar-Mojarad, M. Liakata
Journal of Biomedical Semantics 4(1), 5, BioMed Central Ltd, 2013
R.D. Boyce, J.R. Horn, O. Hassanzadeh, A. de Waard, J. Schneider, J.S. Luciano, M. Rastegar-Mojarad, M. Liakata
Journal of Biomedical Semantics 4(1), 5, BioMed Central Ltd, 2013
2012
Instance-Based Matching of Large Ontologies Using Locality-Sensitive Hashing
S. Duan, A. Fokoue, O. Hassanzadeh, A. Kementsietsidis, K. Srinivas, M. Ward
The Semantic Web--ISWC 2012, 49--64, Springer
S. Duan, A. Fokoue, O. Hassanzadeh, A. Kementsietsidis, K. Srinivas, M. Ward
The Semantic Web--ISWC 2012, 49--64, Springer
Data Management Issues on the Semantic Web
O. Hassanzadeh, A. Kementsietsidis, Y. Velegrakis
Data Engineering (ICDE), 2012 IEEE 28th International Conference on, pp. 1204--1206
O. Hassanzadeh, A. Kementsietsidis, Y. Velegrakis
Data Engineering (ICDE), 2012 IEEE 28th International Conference on, pp. 1204--1206
Publishing Bibliographic Data on the Semantic Web using BibBase
Reynold S. Xin, Oktie Hassanzadeh, Christian Fritz, Shirin Sohrabi and Renee J. Miller
Semantic Web, IOS Press, 2012
Reynold S. Xin, Oktie Hassanzadeh, Christian Fritz, Shirin Sohrabi and Renee J. Miller
Semantic Web, IOS Press, 2012
Semantic Link Discovery over Relational Data
Oktie Hassanzadeh, Anastasios Kementsietsidis, Lipyeow Lim, Renee J. Miller, and Min Wang
Semantic Search over the Web, pp. 193-224, Springer, 2012
Oktie Hassanzadeh, Anastasios Kementsietsidis, Lipyeow Lim, Renee J. Miller, and Min Wang
Semantic Search over the Web, pp. 193-224, Springer, 2012
2011
Linking Semistructured Data on the Web.
Oktie Hassanzadeh, Soheil Hassas Yeganeh, Ren{'e}e J Miller
WebDB, 2011
Oktie Hassanzadeh, Soheil Hassas Yeganeh, Ren{'e}e J Miller
WebDB, 2011
Linked open drug data for pharmaceutical research and development
M. Samwald, A. Jentzsch, C. Bouton, C. Kalles\oe, E. Willighagen, J. Hajagos, M. Marshall, E. Prud'hommeaux, O. Hassanzadeh, E. Pichler, others
Journal of cheminformatics 3(1), 19, Chemistry Central Ltd, 2011
M. Samwald, A. Jentzsch, C. Bouton, C. Kalles\oe, E. Willighagen, J. Hajagos, M. Marshall, E. Prud'hommeaux, O. Hassanzadeh, E. Pichler, others
Journal of cheminformatics 3(1), 19, Chemistry Central Ltd, 2011
Helix: Online Enterprise Data Analytics
Oktie Hassanzadeh, Songyun Duan, Achille Fokoue, Anastasios Kementsietsidis, Kavitha Srinivas, Michael J Ward
WWW (Companion Volume), pp. 225-228, ACM, 2011
Abstract
Oktie Hassanzadeh, Songyun Duan, Achille Fokoue, Anastasios Kementsietsidis, Kavitha Srinivas, Michael J Ward
WWW (Companion Volume), pp. 225-228, ACM, 2011
Abstract
Linking Semistructured Data on the Web
S. Hassas Yeganeh, O. Hassanzadeh, R. J. Miller
Proceedings of the 14th International Workshop on the Web and Databases (WebDB 2011)
S. Hassas Yeganeh, O. Hassanzadeh, R. J. Miller
Proceedings of the 14th International Workshop on the Web and Databases (WebDB 2011)
2010
Publishing Bibliographic Data on the Semantic Web using BibBase
Reynold S. Xin, Oktie Hassanzadeh, Christian Fritz, Shirin Sohrabi, Yang Yang, Jiang Du, Minghua Zhao, Ren\'ee J. Miller
Proceedings of the 9th International Semantic Web Conference (ISWC-10), Poster \& Demo Track, pp. 15--22, IOS Press, 2010
Reynold S. Xin, Oktie Hassanzadeh, Christian Fritz, Shirin Sohrabi, Yang Yang, Jiang Du, Minghua Zhao, Ren\'ee J. Miller
Proceedings of the 9th International Semantic Web Conference (ISWC-10), Poster \& Demo Track, pp. 15--22, IOS Press, 2010
BibBase Triplified
O Hassanzadeh, R S Xin, C Fritz, Y Yang, J Du, M Zhao, R J Miller
Proceedings of the 6th International Conference on Semantic Systems, pp. 41, 2010
O Hassanzadeh, R S Xin, C Fritz, Y Yang, J Du, M Zhao, R J Miller
Proceedings of the 6th International Conference on Semantic Systems, pp. 41, 2010
Online Annotation of Text Streams with Structured Entities
K Q Pu, O Hassanzadeh, R Drake, R J Miller
Proceedings of the 19th ACM international conference on Information and knowledge management, pp. 29--38, 2010
K Q Pu, O Hassanzadeh, R Drake, R J Miller
Proceedings of the 19th ACM international conference on Information and knowledge management, pp. 29--38, 2010
2009
Linking Open Drug Data.
Anja Jentzsch, Jun Zhao, Oktie Hassanzadeh, Kei-Hoi Cheung, Matthias Samwald, Bosse Andersson
I-SEMANTICS, 2009
Anja Jentzsch, Jun Zhao, Oktie Hassanzadeh, Kei-Hoi Cheung, Matthias Samwald, Bosse Andersson
I-SEMANTICS, 2009
A framework for semantic link discovery over relational data
Oktie Hassanzadeh, Anastasios Kementsietsidis, Lipyeow Lim, Ren\'ee J Miller, Min Wang
Proceedings of the 18th ACM conference on Information and knowledge management, pp. 1027--1036, 2009
Oktie Hassanzadeh, Anastasios Kementsietsidis, Lipyeow Lim, Ren\'ee J Miller, Min Wang
Proceedings of the 18th ACM conference on Information and knowledge management, pp. 1027--1036, 2009
Linkage Query Writer
O Hassanzadeh, R Xin, R J Miller, A Kementsietsidis, L Lim, M Wang
Proceedings of the 35th International Conference on Very Large Data Bases (VLDB 2009)-Demonstrations Track, pp. 1590--1593, VLDB Endowment
O Hassanzadeh, R Xin, R J Miller, A Kementsietsidis, L Lim, M Wang
Proceedings of the 35th International Conference on Very Large Data Bases (VLDB 2009)-Demonstrations Track, pp. 1590--1593, VLDB Endowment
LinkedCT: A Linked Data Space for Clinical Trials
O Hassanzadeh, A Kementsietsidis, L Lim, R J Miller, M Wang
Arxiv preprint arXiv:0908.0567, 2009
O Hassanzadeh, A Kementsietsidis, L Lim, R J Miller, M Wang
Arxiv preprint arXiv:0908.0567, 2009
Creating Probabilistic Databases from Duplicated Data
O. Hassanzadeh, R. J. Miller
The VLDB Journal 18(5), 1141--1166, Springer-Verlag New York, Inc., 2009
O. Hassanzadeh, R. J. Miller
The VLDB Journal 18(5), 1141--1166, Springer-Verlag New York, Inc., 2009
Framework for Evaluating Clustering Algorithms in Duplicate Detection
O Hassanzadeh, F Chiang, H C Lee, R J Miller
Proceedings of the VLDB Endowment 2(1), 1282--1293, VLDB Endowment, 2009
O Hassanzadeh, F Chiang, H C Lee, R J Miller
Proceedings of the VLDB Endowment 2(1), 1282--1293, VLDB Endowment, 2009
A Declarative Framework for Semantic Link Discovery over Relational Data
O Hassanzadeh, L Lim, A Kementsietsidis, M Wang
Proceedings of the 18th International Conference on World wide web, pp. 1101--1102, ACM, 2009
O Hassanzadeh, L Lim, A Kementsietsidis, M Wang
Proceedings of the 18th International Conference on World wide web, pp. 1101--1102, ACM, 2009
Linking Open Drug Data
A Jentzsch, J Zhao, O Hassanzadeh, K H Cheung, M Samwald, B Andersson
Proceedings of the Second Triplification Challenge 2009, Graz, Austria
A Jentzsch, J Zhao, O Hassanzadeh, K H Cheung, M Samwald, B Andersson
Proceedings of the Second Triplification Challenge 2009, Graz, Austria
Enabling Tailored Therapeutics with Linked Data
A Jentzsch, O Hassanzadeh, C Bizer, B Andersson, S Stephens
Proceedings of the 2nd Workshop on Linked Data on the Web (LDOW2009)
A Jentzsch, O Hassanzadeh, C Bizer, B Andersson, S Stephens
Proceedings of the 2nd Workshop on Linked Data on the Web (LDOW2009)
Linked Movie Data Base
O Hassanzadeh, M Consens
Proceedings of the 2nd Workshop on Linked Data on the Web (LDOW2009)
O Hassanzadeh, M Consens
Proceedings of the 2nd Workshop on Linked Data on the Web (LDOW2009)
2007
Accuracy of Approximate String Joins Using Grams.
Oktie Hassanzadeh, Mohammad Sadoghi, Ren{'e}e J Miller
QDB, pp. 11--18, 2007
Oktie Hassanzadeh, Mohammad Sadoghi, Ren{'e}e J Miller
QDB, pp. 11--18, 2007
Accuracy of Approximate String Joins Using Grams
Oktie Hassanzadeh, Mohammad Sadoghi, Renee J. Miller
Proceedings of the Fifth International Workshop on Quality in Databases, QDB 2007, at the VLDB 2007 conference, Vienna, Austria, September 23, 2007, pp. 11-18
Oktie Hassanzadeh, Mohammad Sadoghi, Renee J. Miller
Proceedings of the Fifth International Workshop on Quality in Databases, QDB 2007, at the VLDB 2007 conference, Vienna, Austria, September 23, 2007, pp. 11-18
Benchmarking declarative approximate selection predicates
Amit Chandel, Oktie Hassanzadeh, Nick Koudas, Mohammad Sadoghi, Divesh Srivastava
Proceedings of the ACM SIGMOD International Conference on Management of Data, Beijing, China, June 12-14, 2007, pp. 353-364
Amit Chandel, Oktie Hassanzadeh, Nick Koudas, Mohammad Sadoghi, Divesh Srivastava
Proceedings of the ACM SIGMOD International Conference on Management of Data, Beijing, China, June 12-14, 2007, pp. 353-364