1. A computer implemented method of amending an object oriented model comprising the steps of: identifying a first object or group of objects to be added to the model; identifying a second object or group of objects to be replaced by said first object or group of objects; interrogating the model to retrieve information defining the relationships between said second object or group of objects and other components of said model; and using said relationship definitions to configure said first object or group of objects within said model so as to assume corresponding relationships with said other components.