Visual Language (VL) system development is getting increasingly sophisticated in part due to the arduous nature of user interface (UI) code development. This typically involves idiosyncratic calls to the windowing system that are intertwined with the rest of the logic of the VL system. To achieve an effective separation of the intertwined code, we take our cue from memory-mapped display for character based terminals and use a datamapped architecture where all entities on the screen are mapped into data in the system. The computation of what is on the screen or changes to it can then be viewed as querying or updating this data respectively. We propose a declarative language, called HiD++, to implement this architecture that in addition to naturally expressing query and update computations, also addresses many other software engineering concerns. We have used HiD++ to implement a system for a visual langage called RenderingBy-Example (RBE) and report our experiences here. This work has ...