1. A method for comparing models, comprising: using a computer to compare first and second models; using the computer to generate a comparison model comprising each object of the first and second models, the comparison model indicating differences between the first model and the second model, the comparison model comprising a comparison node for each object of the first and second models, each comparison node including a comparison state indicating a state of equality or inequality between the first and second models for a particular object; using a notification manager to register the comparison model as a subscriber of the first and second models; updating the first model to reflect a designated change; upon successful completion of the first designated change to an object of the first model, using the notification manager to issue a notification of the designated change to the comparison model; in response to each modification of an object in the first model, using the computer to synchronously update in real time the comparison model and the second model to reflect the first designated change for a substantially synchronous modification of the first, second, and comparison models; and displaying the comparison model on a client.