1. A method for extending a visualization platform, the method comprising: providing a visualization authoring environment configured to enable a developer to define a user interface appearance and behavior of a prospective software application or a prospective modification to an existing software application at least in part by incorporating native widgets; storing such definitions on computer readable media in a format that can be utilized by one or more other instances of the visualization authoring environment and/or one or more instances of a visualization rendering environment; providing in the visualization authoring environment a facility to enable a user to incorporate one or more non-native widgets into the visualization authoring environment without requiring acquisition or installation of a new version of the visualization authoring environment; providing in the visualization authoring environment a facility to enable the user to incorporate non-native widgets into a visualization project; encapsulating computer readable instructions for an appearance and/or behavior of one or more non-native widgets into the visualization project at least partly in response to a user action; providing in the visualization authoring environment a facility to enable the user to modify one or more of the following attributes of an instance of a non-native widget: size, position, connections between the non-native widget and other widgets; and providing in a visualization rendering environment a facility to exhibit the desired visual rendering and/or interactive behavior during rendering of the visualization project to thereby simulate the proposed software application.