1. A method comprising: receiving, from an application running on a computing device, a request for a user interface (UI) resource item, the request having one or more associated request conditions, the UI resource item generically identifying a UI resource and the UI resource item having multiple UI resource instances, each UI resource instance identifying a particular value for the UI resource item as well as one or more resource instance conditions under which the particular value for the UI resource item is appropriate, each of the one or more associated request conditions having different weights; determining, at a decision module of the computing device and using a resource index that includes the multiple UI resource instances of the UI resource item on the computing device, one of the multiple UI resource instances that includes one or more resource instance conditions that satisfy the request conditions, the request conditions identifying one or more display characteristics desired by the application, the determining including applying the different weights of the one or more associated request conditions, wherein the determining further comprises determining whether one or more of the multiple UI resource instances have resource instance conditions that satisfy all of the request conditions, and identifying as the one UI resource instance a most appropriate UI resource instance of the multiple UI resource instances in response to one or more of the multiple UI resource instances not having resource conditions that satisfy all of the request conditions; and returning, from the decision module, the one UI resource instance to the application.