Team

Prof. Dr. Kathrin Klamroth (Uni Wuppertal)
Dr. Andreia Guerreiro (INESC-ID Lisbon)

Prof. Dr. José Rui Figueira (IST Lisbon)
Prof. Dr. Carlos Fonseca (Universität Coimbra)
Philipp Herrmann (RPTU Kaiserslautern-Landau)
Prof. Dr. Luís Paquete (Universität Coimbra)
Prof. Dr. Stefan Ruzika (RPTU Kaiserslautern-Landau)
PD Dr. Michael Stiglmayr (Uni Wuppertal)
Dr. Julia Sudhoff Santos (Uni Wuppertal)

Projekt

Ordinal combinatorial optimization (OCO) problems can be best motivated by an application example. Consider the problem of planning safe and convenient bicycle routes for every-day travel. In this context, we distinguish between safe streets (green: reserved for cyclists), medium-safe streets (orange: having a reasonably safe bicycle lane), and unsafe streets (red: busy streets without a bicycle lane). Assuming that green is better than orange, and that orange is better than red, a path with one green and one orange edge (g,o) is clearly preferred over a path with one green and one red edge (g,r). However, when comparing a path with orange, orange (o,o) with a path with green, red (g,r), a ranking depends on the individual preferences of the decision maker. Ordinal combinatorial optimization is concerned with the modelling and analysis of ordering relations in the presence of ordinal criteria, the derivation of ordinally nondominated solutions, and the development as well as implementation of efficient solution methods for different classes of combinatorial optimization problems including shortest paths, network flows, knapsack problems, and assignment problems, among others.

The scientific goal of this project is to advance the theoretical understanding and the algorithmic solution of ordinal combinatorial optmization problems by combining state-of-the-art methods from Computer Science and from Mathematical Optimization for mutual benefit. Simultaneously, we establish and advance an international and cross-disciplinary collaboration between the Universities at Coimbra, Lissabon, Kaiserslautern, and Wuppertal. The project promotes the scientific careers of young and promising researchers by supporting research stays at the respective partner organizations and by integrating master students though the joint supervision of master theses.

Workshop, Meetings, Forschungsaufenthalte

• 22.–28.9.2024 in Coimbra und Lissabon (Stefan Ruzika und Philipp Herrmann)
• 21.–25.10.2024 in Coimbra und Lissabon (Kathrin Klamroth und Michael Stiglmayr)
• 22.–28.1.2025 in Wuppertal (José Rui Figueira und João Almeida)
• 19.–25.10.2025 in Wuppertal (Gonçalo Lopes in Wuppertal)
• 10.–12.12.2025 in Coimbra (Jannette Faßbeck und Cansu Kilic)
• 25.–29.1.2026 in Coimbra (Chiara Weuste)
• 26.–29.1.2026 in Coimbra (Rabea Freese)
• 16.–20.3.2026 in Coimbra (Stefan Ruzika)
• 22.–26.3.2026 in Wuppertal (Andreia Guerreiro)

Konferenz-Vorträge

1. J. Sudhoff Santos: "A Divide-And-Conquer Approach for Polyhedral Dominance Cones: Bridging the Gap from General Order Relations to Practical Problem Solving", MCDM 2024, Hammamet, June 6, 2024
2. K. Klamroth: "Ordinal Location Problems and Consistent Multiobjective Shortest Paths", MCDM 2024, Hammamet, June 6, 2024
3. Kathrin Prinz: „The Parallel Epsilon-Algorithm for Tri-Objective Integer Optimization Problems“ RAMOO 2024, Wuppertal
4. Philipp Herrmann: „Axiomatic Foundations and Polyhedral Characterizations for Ordinal Optimization“, OR2025, Bielefeld
5. Levin Nemesch: „Modern Algorithms in Old Literature: What Can Multi-Objective Optimization Learn from Parametric Optimization?“, OR2025, Bielefeld
6. M. Stiglmayr "Computation of Safe Routes to School", Kaiserslautern Applied and Industrial Mathematics Days, October 6–8, 2025

Abschlussarbeiten

• Renée Lamsfuß: "Ordinal Location Problems with Consistent Multiobjective Shortest Paths". Master Thesis, Bergische Universität Wuppertal, 04/2024
• Philipp Herrmann: “Ordinal Optimization Problems", RPTU Kaiserslautern-Landau 02/2025
• Dorotea Redzepi: “Weight Set Decomposition for the Multiobjective Minimum Spanning Tree Problem” 05/2026
• Marian Mayer: "Finding all Nondominated Images of Multicriteria Optimization Problems using the Tchebycheff Scalarization", RPTU Kaiserslautern-Landau 01/2026
• Laura Klingel: "The Ordinal Shortest Path Problem on Multi-Modal Networks", RPTU Kaiserslautern-Landau (expected 05/2026)
• Johanna Hochsprung: “The Multimodal Traveling Salesman Problem under Regular-Language Constraints”, RPTU Kaiserslautern-Landau (expected 05/2026)
   

Promotionen

• Kathrin Prinz: Parallelization in Multi-Objective Optimization Based on the Epsilon-Constraint Scalarization, RPTU Kaiserslautern-Landau (02/2026)
• Kezang Yuden: Parametric Biobjective Linear Programming, RPTU Kaiserslautern-Landau (03/2026)