Research

• General Research Topics: Data Mining & Machine Learning, Information Security Management, Information Filtering, Applications of AI and OR Techniques in Business, Database
• Specific Research Topics: Isotonic Data Separation for Medical Diagnosis, Web Information Filtering, etc., Computer Intrusion Detection, Recommendation Systems and Personalization, Schumpeterian Competition and Technology Strategy, Constrained Deductive Database, Formal Modeling of Legal Decision Procedure, Constraint Satisfaction Applications to Decision Sciences, Defeasible Deontic Modeling of Bureaucracy Policies and Procedures, Logic Modeling Approach to Trade Market Optimization, Logical Specifications of Resource Consumption and Production, Formal Business Communications.

1. S.K. Dewitz, Y.U. Ryu, & R.M. Lee. "Defeasible Reasoning in Law," Decision Support Systems, Vol. 11, No. 2, pp. 133-155, 1994.
2. Y.U. Ryu & R.M. Lee. "Defeasible Deontic Reasoning and Its Applications to Normative Systems," Decision Support Systems, Vol. 14, No. 1, pp. 59-73, 1995.
3. R.M. Lee & Y.U. Ryu. "DX: A Deontic Expert System," Journal of Management Information Systems, Vol. 12, No. 1, pp. 145-169, 1995.
4. Y.U. Ryu. "Conditional Deontic Logic Augmented with Defeasible Reasoning," Data & Knowledge Engineering, Vol. 16, No. 1, pp. 73-91, 1995.
5. Y.U. Ryu. "A Hierarchical Constraint Logic Modeling of Multilateral Trade Matching in a Commodity Auction Market," Annals of Operations Research, Information Systems and Operations Research, Part I: Models of Systems (R. Ramesh and H. R. Rao, Editors), Vol. 71, pp. 317-334, 1997.
6. Y.U. Ryu. "Logic Based Representation and Reasoning about Knowledge of Constrained Resources," Knowledge-Based Systems, Vol. 10, No. 2, pp. 71-80, 1997.
7. Y.U. Ryu. "Constraint Logic Programming Framework for Integrated Decision Support," Decision Support Systems, Vol. 22, No. 2, pp. 155-170, 1998.
8. Y.U. Ryu. "Specification of Contractual Obligations in Formal Business Communication," Data & Knowledge Engineering, Vol. 26, No. 3, pp. 309-326, 1998.
9. Y.U. Ryu. "Logic-Based Modeling of Resource Consumption and Production," Decision Support Systems, Vol. 22, No. 3, pp. 243-257, 1998.
10. Y.U. Ryu & S.-C. Hong. "A Computational Model of Continuous Trading in Auction Markets: A Parallel Expert System Approach," New Review of Applied Expert Systems, Vol. 4, pp. 33-45, 1998.
11. Y.U. Ryu. "A Hierarchical Constraint Satisfaction Approach to Product Selection for Electronic Shopping Support." IEEE Transactions on Systems, Man, and Cybernetics (Part A: Systems and Humans), Vol. 29, No. 6, pp. 525-532, 1999.
12. J. Lee & Y.U. Ryu. "Exploration, Exploitation, and Adaptive Rationality: The Neo-Schumpeterian Perspective." Simulation Modelling Practice and Theory, Vol. 10, Nos. 5-7, pp. 297-320, 2002.
13. Y.U. Ryu, R. Chandrasekaran, & V. Jacob. "Prognosis Using an Isotonic Prediction Technique," Management Science, Vol. 50, No. 6, pp. 777-785, 2004.
14. I. Choi, H. Jung, M. Song, & Y.U. Ryu "IPM-EPDL: An XML-Based Executable Process Definition Language," Computers in Industry, Vol. 56, No. 1, pp. 85-104, 2005.
15. Y.U. Ryu & W.T. Yue. "Firm Bankruptcy Prediction: Experimental Comparison of Isotonic Separation and Other Classification Approaches," IEEE Transactions on Systems, Man, and Cybernetics (Part A: Systems and Humans), Vol. 35, No. 5, pp. 727-737, 2005.
16. R. Chandrasekaran, Y.U. Ryu, V. Jacob, & S. Hong. "Isotonic Separation," INFORMS Journal on Computing, Vol. 17, No. 4, pp. 462-474, 2005.
17. V. Jacob, R. Krishnan, & Y.U. Ryu. "Internet Content Filtering Using Isotonic Separation on the PICS Specification," ACM Transactions on Internet Technology, Vol. 7, No. 1, Article No. 1, 2007.
18. Y.U. Ryu, R. Chandrasekaran, & V. Jacob. "Data Classification Using the Isotonic Seeparation Technique: Application to Breast Cancer Prediction," European Journal of Operational Research, Vol. 181, No. 2, pp. 842-854, 2007.
19. W.T. Yue, M. Cakanyildirim, Y.U. Ryu & D. Liu. "Network Externalities, Layered Protection and IT Security Risk Management," Decision Support Systems, Vol. 44, No. 1, pp. 1-16, 2007.
20. Y.U. Ryu & H.-S. Rhee. "Improving Intrusion Prevention Models: Dual-Threshold and Dual-Filter Approaches," INFORMS Journal on Computing, Vol. 20, No. 3, pp. 356-367, 2008.
21. Y.U. Ryu & H.-S. Rhee. "Evaluation of Intrusion Detection Systems under an Inspection Constraint," ACM Transactions on Information and System Security, Vol. 11, No. 4, Article No. 20, 2008.
22. W.T. Yue, M. Cakanyildirim, & Y.U. Ryu. "The Management of Intrusion Detection: Configuration, Inspection, and Investment," European Journal of Operational Research, Vol. 195, No. 1, pp. 186-204, 2009.
23. M. Mannino, Y. Yang, & Y.U. Ryu. "Classification Algorithm Sensitivity to Training Data with Non Representative Attribute Noise," Decision Support Systems, Vol. 46, No. 3, pp. 743-751, 2009.
24. H.K. Kim, J.K. Kim, & Y.U. Ryu. "Personalized Recommendation over a Customer Network for Ubiquitous Shopping," IEEE Transactions on Services Computing, Vol. 2, No. 2, pp. 140-151, 2009.
25. H.-S. Rhee, C.-T. Kim, & Y.U. Ryu. "Self-Efficacy in Information Security: Its Influence on End Users' Information Security Practice Behavior," Computers & Security, Vol. 28, No. 8, pp. 816-826, 2009.
26. J. Lee, S.H. Park, Y.U. Ryu & Y.S. Baik. "A Hidden Cost of Strategic Alliances under Schumpeterian Dynamics," Research Policy, Vol. 39, No. 2, pp. 229-238, 2010.
27. J.K. Kim, H.K. Kim, H.Y. Oh, & Y.U. Ryu. "A Group Recommendation System for Online Communities," International Journal of Information Management, Vol. 30, No. 3, pp. 212-219, 2010.
28. H.K. Kim, Y.U. Ryu, Y. Cho, & J.K. Kim. "Customer-Driven Content Recommendation over a Network of Customers," IEEE Transactions on Systems, Man, and Cybernetics (Part A: Systems and Humans), Forthcoming.
29. M. Chen & Y.U. Ryu. "Improving Web Site Structure to Facilitate Effective User Navigation," IEEE Transactions on Knowledge and Data Engineering, forthcoming.
30. H.-S. Rhee, Y.U. Ryu, & C.-T. Kim. "Unrealistic Optimism on Information Security Management," Computers & Security, forthcoming.

1. R.M. Lee & Y.U. Ryu. "Event Grammars: A Modeling Representation for Business Procedures," in Proceedings of the 22nd Hawaii International Conference on System Sciences, Vol. 2, pp. 553-559, 1989.
2. Y.U. Ryu. "Tuning Database Management Systems to Management Information Systems (Extended Abstract)," in Proceedings of the 2nd International Conference of the Information Resource Management Association, 1991.
3. Y.U. Ryu & R.M. Lee. "Defeasible Deontic Reasoning: A Logic Programming Model," in Proceedings of the 1st International Workshop on Deontic Logic in Computer Science, Amsterdam, The Netherlands, pp. 347-363, 1991.
4. Y.U. Ryu. "Logical Specification of Resource Consumption and Production," in Proceedings of the 29th Hawaii International Conference on System Sciences, Vol. 2, pp. 39-46, 1996.
5. Y.U. Ryu. "Relativized Deontic Modalities for Contractual Obligations in Formal Business Communication," in Proceedings of the 30th Hawaii International Conference on System Sciences, Vol. 4, pp. 485-493, 1997.
6. Y.U. Ryu. "Approximate Constraint Satisfaction over a Constraint Hierarchy: A Preliminary Study," in Proceedings of the 31st Hawaii International Conference on System Sciences, Vol. 5, pp. 134-141, 1998.
7. Y.U. Ryu. "Dynamic Construction of Product Taxonomy Hierarchies for Assisted Shopping in Electronic Marketplaces," in Proceedings of the 31st Hawaii International Conference on System Sciences, Vol. 5, pp. 196-204, 1998.
8. Y.U. Ryu & S.-C. Hong. "Negotiation Support in a Commodity Trading Market," in Proceedings of the 31st Hawaii International Conference on System Sciences, Vol. 5, pp. 233-241, 1998.
9. V. Jacob, R. Krishnan, Y.U. Ryu, R. Chandrasekaran, & S. Hong. "Filtering Objectionable Internet Content," in Proceedings of the 20th International Conference on Information Systems, pp. 274-278, 1999.
10. Y.U. Ryu, R. Chandrasekaran, & V. Jacob. "Disease Prognosis with an Isotonic Prediction Technique," in Proceedings of the 9th Workshop on Information Technologies and Systems, pp. 26-31, 1999.
11. W.T. Yue, M. Cakanyildirim, Y.U. Ryu, & D. Liu. "IT Security Risk Management under Network Effects and Layered Protection Strategy," in Proceedings of the 2nd Symposium on Intelligence and Security Informatics, 2004.
12. H.-S. Rhee, Y.U. Ryu, & C.-T. Kim. "I Am Fine but Your Are Not: Optimistic Bias and Illusion of Control on Information Security," in Proceedings of the 26th International Conference on Information Systems, 2005.
13. Y.U. Ryu & H.-S. Rhee. "Operational Models of Intrusion Prevention Systems," in Proceedings of the 15th Workshop on Information Technologies and Systems, pp. 63-68, 2005.
14. Y.U. Ryu, H.K. Kim, Y.H. Cho, & J.K. Kim. "Peer-Oriented Content Recommendation in a Social Network," in Proceedings of the 16th Workshop on Information Technology and Systems, pp. 115-120, 2006.
15. M.V. Mannino, Y. Yang, & Y.U. Ryu. "Classification Algorithm Sensitivity to Training Data with Non-Representative Attribute Noise," in Proceedings of the 13th Americas Conference on Information Systems, 2007.
16. Y.U. Ryu, H.K. Kim, J.K. Kim, & Y.H. Cho. "Experimental Evaluation of Recommendation over a Customer Network," in Proceedings of the 17th Workshop on Information Technology and Systems, pp. 158-163, 2007.
17. M. Chen & Y.U. Ryu. "Improving Web Site Structure to Facilitate Effective User Navigation," in Proceedings of the 29th International Conference on Information Systems, 2008.
18. M.V. Mannino, Y. Yang, & Y.U. Ryu. "Understanding the Relationship between Actual and Artificial Deception: Reducing the Cost of Collecting Deceptive Data," to appear in Proceedings of the 18th Workshop on Information Technologies and Systems, pp. 43-48, 2008.
19. S. Lee, Y.U. Ryu, & J.K. Kim. "IT Investment and Economic Performance: A Causality Analysis over Multiple Countries," in Proceedings of the 18th Workshop on Information Technologies and Systems, pp. 230-235, 2008.
20. J.K. Kim, M.K. Jang, H.K. Kim, & Y.U. Ryu. "A Personalized Preference Boundary-Based Procedure for Recommending New Items," in Proceedings of the 8th Workshop on eBusiness, 2009.
21. H.K. Kim, J.K. Kim, & Y.U. Ryu. "A Local Scoring Model for Recommendation," in Proceedings of the 20th Workshop on Information Technologies and Systems, 2010.
22. I.Y. Choi, H.K. Kim, Y.U. Ryu, & J.K. Kim. "A Tourism Recommender System Based on Approximate Constraint Satisfaction," in Proceedings of LC CNS/KrAIS Workshop on the Future of IS Research, 2010.
23. Y.U. Ryu, J.K. Kim, K.H. Im, & H. Hong. "Neural Network Analysis of Right-Censored Observations for Occurrence Time Prediction," in Proceedings of the 10th Workshop on eBusiness, 2011.

1. Y.U. Ryu & R.M. Lee. "Defeasible Deontic Reasoning: A Logic Programming Model," in J.-J.Ch. Meyer & R.J. Wieringa (Editors), Deontic Logic in Computer Science, John Wiley & Sons, pp. 224-241, 1993.
2. Y.U. Ryu & R.M. Lee. "Deontic Logic Viewed as Defeasible Reasoning," in D. Nute (Editor), Defeasible Deontic Logic, Synthese Library Volume 236, Kluwer, pp. 123-137, 1997.

1. I. Choi & Y.U. Ryu. Visual Logic Modeling Environment and Its Application to Network Flow Optimization Problems. Research Report CBDA-162, Center for Business Decision Analysis, The University of Texas at Austin, 1990
2. Y.U. Ryu & R.M. Lee. Defeasible Deontic Reasoning and Its Applications to Normative Systems. Technical Report TR-1992-07-01, Erasmus University Research Institute for Decision and Information Systems (EURIDIS), Erasmus University, Rotterdam, The Netherlands, 1992.
3. Y.U. Ryu & R.M. Lee. A Formal Representation of Normative Systems: A Defeasible Deontic Reasoning Approach. Research Monograph RM-1992-08-01, Erasmus University Research Institute for Decision and Information Systems (EURIDIS), Erasmus University, Rotterdam, The Netherlands, 1992.

1. "Tuning Database Management Systems to Management Information Systems," The 1991 International Conference of Information Resource Management Association, Memphis, TN, 1991.
2. "Defeasible Deontic Reasoning: A Logic Programming Model," The 1st International Workshop on Deontic Logic in Computer Science, Free (Vrije) University, Amsterdam, The Netherlands, 1991.
3. "Logical Specification of Resource Consumption and Production," The 29th Hawaii International Conference on System Sciences, 1996.
4. "Relativized Deontic Modalities for Contractual Obligations in Formal Business Communication," The 30th Hawaii International Conference on System Sciences, 1997.
5. "Specification of Normative Aspects in Decision Support Systems," INFORMS Annual Meeting, Dallas, 1997.
6. "Approximate Constraint Satisfaction over a Constraint Hierarchy: A Preliminary Study," The 31st Hawaii International Conference on System Sciences, 1998.
7. "Dynamic Construction of Product Taxonomy Hierarchies for Assisted Shopping in Electronic Marketplaces," The 31st Hawaii International Conference on System Sciences, 1998.
8. "Negotiation Support in a Commodity Trading Market," The 31st Hawaii International Conference on System Sciences, 1998.
9. "Filtering Objectionable Internet Content," The 20th International Conference on Information Systems, 1999.
10. "Disease Prognosis with an Isotonic Prediction Technique," The 9th Workshop on Information Technologies and Systems, 1999.
11. "Operational Models of Intrusion Prevention Systems," The 15th Workshop on Information Technologies and Systems, 2005.
12. "Peer-Oriented Content Recommendation in a Social Network," The 16th Workshop on Information Technologies and Systems, 2006.
13. "Experimental Evaluation of Recommendation over a Customer Network," The 17th Workshop on Information Technologies and Systems, 2007.
14. "Mining Censored Data and Occurrence Time Prediction," INFORMS Annual Meeting, Washington DC, 2008.
15. "Understanding the Relationship between Actual and Artificial Deception: Reducing the Cost of Collecting Deceptive Data," The 18th Workshop on Information Technologies and Systems, 2008.
16. "IT Investment and Economic Performance: A Causality Analysis over Multiple Countries," The 18th Workshop on Information Technologies and Systems, 2008.
17. "A Personalized Preference Boundary-Based Procedure for Recommending New Items," The 8th Workshop on eBusiness, 2009.
18. "A Local Scoring Model for Recommendation," The 20th Workshop on Information Technologies and Systems, 2010.
19. "Neural Network Analysis of Right-Censored Observations for Occurrence Time Prediction," The 10th Workshop on eBusiness, 2011.

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