Abstract
In this paper we describe the concept of the renewed software package UG, that is used as a flexible simulation framework for the solution of partial differential equations. A general overview of the concepts of the new implementation is given: The modularization of the software package into several libraries libGrid, libAlgebra, libDiscretization and pcl is described and all major modules are discussed in detail. User backends through scripting and visual editing are briefly considered and examples show the new features of the current implementation.