This page gives details of my research projects in the area of Computing. If you would like more information about any of the projects including questions about research publications or presentations, please contact me.

Constraint Satisfaction Problems are solved by algorithms assigning values (from a domain) to variables in the problem so that all constraints are satisfied. In Distributed Constraint Satisfaction Problems, variables are represented by agents who have only a partial understanding of the problem (their understanding is limited to the variables they represent and the constraints that those variables are involved in). Distributed problems are important when information cannot be shared either because there is too much information or because of privacy concerns. Existing algorithms for Distributed Constraint Satisfaction can be categorised as backtracking and local search algorithms. The former, whilst able to guarantee completeness, are often too slow for practical use whilst the later are often able to converge to a solution quicker but may not solve all problems (i.e. they are incomplete). In my doctoral research, I investigated and developed hybrid algorithms for Distributed Constraint Satisfaction, combining the convergence abilities of local search with the completeness of backtracking. This has led to the development of new algorithms for Distributed Constraint Satisfaction including PenDHyb, Multi-Hyb und Multi-HDCS. My thesis can be downloaded here. Dates: October 2006 to March 2010 (PhD awarded). Supervisor(s): Dr. Ines Arana, Dr. Hatem Ahriz and Dr. Kit-Ying Hui.

LEE, D. and ARANA, I. and AHRIZ, H. and HUI, K. 2010. Multi-HDCS: Solving DisCSPs With Complex Local Problems Cooperatively. In: Proceedings of 2010 IEEE/WIC/ACM International Conference on Intelligent Agent Technology (IAT 2010). 1st-3rd September 2010. Toronto: Canada. pp. 295-302.

LEE, D. and ARANA, I. and AHRIZ, H. and HUI, K. 2009. Multi-Hyb: A Hybrid Algorithm for Solving DisCSPs with Complex Local Problems. In: Proceedings of 2009 IEEE/WIC/ACM International Conference on Intelligent Agent Technology (IAT 2009). 15th-18th September 2009. Milan: Italy. pp. 379-382.

LEE, D. and ARANA, I. and AHRIZ, H. and HUI, K. 2009. A Hybrid Approach to Solving Coarse-grained DisCSPs. In: Proceedings of the Eighth International Conference on Autonomous Agents and Multi-Agent Systems (AAMAS 2009). 10th-15th May 2009. Budapest, Hungary. pp. 1235-1236.

LEE, D. and ARANA, I. and AHRIZ, H. and HUI, K. 2008. A Hybrid Approach to Distributed Constraint Satisfaction. In: D. DOCHEV, M. PISTORE and P. TRAVERSO, ed. Artificial Intelligence: Methodology, Systems and Applications. 13th International Conference, AIMSA 2008 Varna, Bulgaria, September 4-6 2008 Proceedings. 4th-6th September 2008. Varna: Bulgaria. pp. 375-379.

Hybrid Algorithms for Distributed Constraint Satisfaction (Presentation of thesis to thesis committee on 26th March 2010.)

Multi-Hyb: A Hybrid Algorithm for Solving DisCSPs with Complex Local Problems (Presentation of a paper at IAT 2009 in September 2009.)

Hybrid Algorithms for Solving Distributed Constraint Satisfaction Problems (Seminar at the Free University of Berlin, Germany on 25th May 2009.)

A Hybrid Approach to Solving Coarse-grained DisCSPs (Presentation of a paper at AAMAS 2009 in May 2009.)

Cooperative Approaches to Solving Distributed Constraint Satisfaction Problems(Seminar at the Zuse Research Institute Berlin, Germany on 5th May 2009.)

Hybrid Algorithms for Solving Distributed Constraint Satisfaction (Seminar at the School of Computing, The Robert Gordon University, Aberdeen, Scotland on 27th February 2009.)

A Hybrid Approach to Distributed Constraint Satisfaction (Presentation of a paper at AIMSA 2008 in September 2008.)

Constraint-Based Local Search (Presentation of my experiences from a Graduate Course in Constraint-Based Local Search which I attended in June 2007. Presented to the Knowledge Based Systems Research Group in the School of Computing, The Robert Gordon University, Aberdeen, Scotland on 22nd October 2007.)

DisPBJ: A Hybrid Algorithm for Distributed Constraint Solving. (Presented to the Knowledge Based Systems Research Group in the School of Computing, The Robert Gordon University, Aberdeen, Scotland on 3rd May 2007.)

Distributed Constraint Satisfaction: Justification of Research Interests. (PG Cert Research Methods Module 1 Presentation on 27th October 2006.)

Queens in Chess: A demonstrator shown to research visitors at the Robert Gordon University to explain the process of solving the N Queens Constraint Satisfaction Problem. The software is written (in Java) as a playable game whilst the user can elect to get the computer to solve the problem at any time.

Timetable Scheduler: A Java meeting scheduling tool. The software uses one of the algorithms developed during my PhD research, Multi-Hyb, to determine the solution to the current problem.

Additionally I extended SIDCOT and SEICOSSA which were developed in other research projects to use the new algorithms developed during my doctoral research.

Facilitating the input of a model which ensures efficiency during the search for a solution is no easy task. Additionally, presenting the solution to the user so that they can understand it is also not trivial. Therefore, I designed SIDCOT as my Honours Individual Project for my Computing for Business and E-Commerce honours degree. The software provides a wizard-style interface which guides the user from problem modelling (as a Constraint Satisfaction Problem) through problem solving to the display of the solution with minimal constraint programming knowledge. The project exceeded all aims and objectives and, consequently, was awarded the highest grade. (The software was updated and extended during my doctoral research to use the new algorithms I developed during my PhD.) Dates: September 2005 to April 2006 (part-time). Supervisor(s): Dr. Ines Arana

SIDCOT: A Smart Interface for Constraint Programming. (Honours Project Presentation on 26th April 2006.)

Currently there is no one algorithm which is capable of solving all Distributed Constraint Satisfaction problems. However, a number of algorithms do exist which are suited to different problems. This project compared the Distributed Breakout Algorithm with the Distributed Stochastic Algorithm on randomly-generated problems and scheduling problems. Our tentative conclusions suggested that the Distributed Breakout Algorithm was more suited to randomly-generated problems whilst the Distributed Stochastic Algorithm performed better on scheduling problems. A prize was awarded for the research undertaken during this project. In addition to my research, I developed an experimental workbench written in Java to compare Distributed Constraint Satisfaction algorithms. This experimental workbench (SEICOSSA – A Smart Experimental Interface for Constraints) was also used and further developed during my doctoral research.Dates: May to September 2005. Supervisor(s): Dr. Ines Arana and Dr. Hatem Ahriz.

A Comparison of Two Distributed Constraint Saitsfaction Algorithms. (RDI Summer Scholarship Presentation in September 2005.)

SEICOSSA – A Smart Experimental Interface for Constraints: which compares various „Distributed Constraint Satisfaction“ algorithms.

How effective is relevance profiling in retrieving relevant pages of a book as defined by the book’s own index? This project sought to measure this effectiveness through an investigation of a number of weighting functions on the within-document retrieval tool, ProfileSkim. The project was fully funded by the Robert Gordon University. Conclusions from the project were presented at the Ninth Australasian Document Computing Symposium. Dates: June to September 2004. Supervisor(s): Professor David J Harper.

ProfileSkim: Experiments with Relevance Profiling. (Presented to the Information Retrieval and Interaction Research Group in the School of Computing, The Robert Gordon University, Aberdeen, Scotland in September 2004.)

HARPER, D. J. and LEE, D. 2004. On the Effectiveness of Relevance Profiling. In: P. BRUZA, A. MOFFAT and A. TURPIN, ed. Proceedings of the Ninth Australasian Document Computing Symposium. 13th December 2004. Melbourne: Australia. pp. 10-16.