Model-based user-interface development has been characterized as a process of creating mappings between elements in various mo

The incorporation of plastic and adaptive user-interfaces into the model-based paradigm requires a new, more flexible modeling formalism. Rather than modeling the user-interface as a set of static structures and mappings, the UI should be modeled as a set of design preferences. Preferences are frequently many-toone or many-to-many relationships that elude conventional UI modeling, which has largely focused on oneto-one mappings. In this paper, a spectrum of preference relations is described, and a new syntax for modeling preference is proposed. This spectrum extends from simple one-to-one bindings to complex design guidelines that can be structured together to implement decision trees. This new representation allows decision trees to be tightly integrated into the user-interface model itself, enhancing their flexibility and power.