A method to analyze impact of changes to a model includes accessing a proposed change to a model. An expression that is relevant to the proposed change is accessed. An instances set associated the expression is obtained. The instance set is evaluated to determine an impact of the proposed change to the model. An application utilizes the expression of a model. An impact analyzer assesses impact of a change to the model by evaluating at least one of the one or more expressions and returning an evaluation set for use by the application.