The lower level mediators perform standard accumulations, selections, and analyses on the data sources. They provide their results both to user interface code and to higher level mediators. We had to implement these lower level mediators first to provide a basic level of functionality for the higher level mediators. These mediators allow users to obtain specific feedback without having to understand the structure of the underlying data. Our planned fourth level of mediators will use domain-specific models about the exercise, the scenario, and causal relationships in the exercise to analyze the data for its probable significance and automatically call the users' attention to what it perceives as the more relevant exercise results.
Mediators support multiple applications of feedback.
Within each level of the mediation hierarchy shown in Figure A-2, multiple mediators may collaborate to produce the desired results. The collaboration among mediators at the same level is well described . Typical mediators are a combination of components that interface to data sources, represent domain knowledge, and draw inferences from the internally represented data and knowledge. Data sources are converted into object instances over which inferences can be performed. Knowledge about the application domain is maintained in declarative representations.