I had recently the honour to assist to the Colloquium in occasion of the retirement of Thomas Ottman.

During the last years Ottmann has been a full professor at the Institute fur Informatik of the University of Freiburg. He has been one of the main founders and promoters of the institute and the faculty of angewandte wissenchaft.

His most relevant scientific contribution is probably the Bentley-Ottmann algorithm, which solves the line segment intersection problem. The algorithm is another evidence of the importance of considering output-sensitive complexity and the convenience of using so-called sweep-line techniques, also applied to other fundamental computational geometry problems (Voronoi diagrams, Delaunay triangulation, etc.). That was impressive for me but he used to said: “I was just the right man and the right moment, that’s all.” Always modest, always professional.

The colloquium had also very interesting invited talks by Amitava Datta (on data-parallel dynamic programing on gpus) and Rolf Klein (on geometric neighborhoods). Both talks had a perfect balance between technical contribution, abstraction level and connection to Ottmann’s contribution.

This post is just my modest way to express my gratitude for giving me the opportunity to get a PhD, and to render honour to one of the most professional persons I have ever encountered.