This example demonstrates reactive data binding with the Model.js library, showing how a full name updates automatically as users type into first and last name input fields. The page contains a simple HTML form where two text inputs feed values into a model instance, and a `model.when` listener combines the firstName and lastName properties into a fullName string. The full name is then rendered into a span element and logged to the console using D3.js selection and text methods. The example illustrates how Model.js tracks property dependencies and triggers callbacks asynchronously.