User Interfaces (UI) of applications, since about 2010, are usually implemented by dedicated frontend programs, following a Rich-Client architecture and are based on the Web technologies HTML, CSS and JavaScript. This approach provides great flexibility and power, but comes with an inherent great overall complexity of UIs, running on a continuously changing technology stack. This is because since over twenty years Web technologies still progress at an extremely high invention rate and unfortunately at the same time still regularly reinvent part of their self. This situation is harmless for small UIs, consisting of just a handful dialogs and having to last for just about one or two years. However, it becomes a major hurdle for large UIs, consisting of a few hundred dialogs and having to last for five or more years. This is especially the case for the complex UIs of industrial Business Information Systems. The main scientific contribution of this dissertation is the Hierarchical User Interface Component Architecture (HUICA), a scalable software architecture for Rich-Client based User Interfaces. It is primarily based on the important architecture principle Separation of Concerns (SoC), the derived idea of Hierarchical Composition, the invented design pattern Model-View-Controller/Component-Tree (MVC/CT) and the existing concepts Presentation Model and Data Binding.