The seminar deals with different concepts of Modulating Function based algebraic observers. After an introduction to the underlying operator form, different estimation tasks are outlined. The considered algebraic observers include the classical approach using UMFs, the usage of observability canonical form as well as the construction via auxiliary problems. Based on that, a linearization framework for a class of nonlinear systems is established. Furthermore, the convolvible nonlinearity perspective is introduced and sketched for robotic problems.