Researchers working with nonlinear programming often claim "the word is non linear" indicating that real applications require nonlinear modeling. The same is true for other areas such as multi-objective programming (there are always several goals in a real application), stochastic programming (all data is uncer tain and therefore stochastic models should be used), and so forth. In this spirit we claim: The word is multilevel. In many decision processes there is a hierarchy of decision makers, and decisions are made at different levels in this hierarchy. One way to handle such hierar chies is to focus on one level and include other levels' behaviors as assumptions. Multilevel programming is the research area that focuses on the whole hierar chy structure. In terms of modeling, the constraint domain associated with a multilevel programming problem is implicitly determined by a series of opti mization problems which must be solved in a predetermined sequence. If only two levels are considered, we have one leader (associated with the upper level) and one follower (associated with the lower level)."

On August 1997 a conference titled "From Local to Global Optimiza- tion" was held at Storgarden in Rimfor.sa near the Linkoping Institute of Technology, Sweden. The conference gave us the opportunity to cel- ebrate Hoang Thy's achievements in Optimization during his 70 years of life. This book consists of a collection of research papers based on results presented during the conference and are dedicated to Professor Hoang Thy on the occasion of his 70th birthday. The papers cover a wide range of recent results in Mathematical Pro- gramming. The work of Hoang Thy, in particular in Global Optimiza- tion, has provided directions for new algorithmic developments in the field. We are indebted to the Kluwer Academic Publishers for inviting us to publish this volume, and the Center for Industrial Information Transfer (CENIIT) for financial support. We wish to thank the referees for their help and the authors for their papers. We also wish to join all contributors of this book in expressing birthday wishes and gratitude to Hoang Thy for his inspiration, support, and friendship to all of us. Athanasios Migdalas, Panos M. Pardalos, and Peter Varbrand November 1998 xv Hoang Tuy: An Appreciation Its a pleasure for me as colleague and friend to take this opportunity to celebrate Hoang 'I\lY'S numerous contributions to the field of mathemat- ical programming.

Researchers working with nonlinear programming often claim "the word is non linear" indicating that real applications require nonlinear modeling. The same is true for other areas such as multi-objective programming (there are always several goals in a real application), stochastic programming (all data is uncer tain and therefore stochastic models should be used), and so forth. In this spirit we claim: The word is multilevel. In many decision processes there is a hierarchy of decision makers, and decisions are made at different levels in this hierarchy. One way to handle such hierar chies is to focus on one level and include other levels' behaviors as assumptions. Multilevel programming is the research area that focuses on the whole hierar chy structure. In terms of modeling, the constraint domain associated with a multilevel programming problem is implicitly determined by a series of opti mization problems which must be solved in a predetermined sequence. If only two levels are considered, we have one leader (associated with the upper level) and one follower (associated with the lower level)."

On August 1997 a conference titled "From Local to Global Optimiza- tion" was held at Storgarden in Rimfor.sa near the Linkoping Institute of Technology, Sweden. The conference gave us the opportunity to cel- ebrate Hoang Thy's achievements in Optimization during his 70 years of life. This book consists of a collection of research papers based on results presented during the conference and are dedicated to Professor Hoang Thy on the occasion of his 70th birthday. The papers cover a wide range of recent results in Mathematical Pro- gramming. The work of Hoang Thy, in particular in Global Optimiza- tion, has provided directions for new algorithmic developments in the field. We are indebted to the Kluwer Academic Publishers for inviting us to publish this volume, and the Center for Industrial Information Transfer (CENIIT) for financial support. We wish to thank the referees for their help and the authors for their papers. We also wish to join all contributors of this book in expressing birthday wishes and gratitude to Hoang Thy for his inspiration, support, and friendship to all of us. Athanasios Migdalas, Panos M. Pardalos, and Peter Varbrand November 1998 xv Hoang Tuy: An Appreciation Its a pleasure for me as colleague and friend to take this opportunity to celebrate Hoang 'I\lY'S numerous contributions to the field of mathemat- ical programming.