An apparatus, a method, and a computer program are provided to enable an engine to employ a plurality of architectures in building and rendering a hierarchical structure, such as a Graphical User Interface (GUI). Currently, engines are typically hard coded to employ a single architecture, thus, requiring the engine to be architecturally specific. However, with the variety of architectures that exist and that are in use, it is useful to have an engine that can interact with many architectures. Therefore, an engine is provided with an interface that allows for interaction with many architectures while maintaining an engine that is architecturally neutral.