  The goal of this work is to describe a categorical formalism for (Extended)
Topological Quantum Field Theories (TQFTs) and present them as functors from a
suitable category of cobordisms with corners to a linear category, generalizing
2d open-closed TQFTs to higher dimensions. The approach is based on the notion
of an n-fold category by C. Ehresmann, weakened in the spirit of monoidal
categories (associators, interchangers, Mac Lane's pentagons and hexagons), in
contrast with the simplicial (weak Kan and complete Segal) approach of Jacob
Lurie. We show how different Topological Quantum Field Theories, such as gauge,
Chern-Simons, Yang-Mills, WZW, Seiberg-Witten, Rozansky-Witten, and AKSZ
theories, as well as sigma model, may be described as functors from the pseudo
n-fold category of cobordisms to a pseudo n-fold category of sets.
