Developing user interfaces for a heterogeneous environment is a difficult challenge. Partial distribution of the user interface is an event harder one. Specifically providing developers with means of describing and controlling how components move around as devices are included or removed We present an approach to overcome these challenges, by combining ontologies with reasoning engines. Our tool MaDoE uses Protégé in combination with Jess to exemplify this in a simulated home setting. Our approach allows system developers to take advantage of the formal knowledge in the ontologies as well harnessing the power of rules inside the expert system when they design distributed user interfaces.