5. A method comprising: registering one or more rules related to an entity associated with a model; receiving input specifying a value of a first attribute associated with the entity; and applying the one or more registered rules to the value of the first attribute to: infer a value of a second attribute associated with the entity or another entity associated with the model, or validate the value of the first attribute or the value of the second attribute.
6. The method of claim 5 , wherein the rules are registered with a modeling application that includes a unit that applies the one or more registered rules to the value of the first attribute.