1. A method for the mass customization of a software artifact, to create one or more variants of said software artifact for different products in a product family, comprising: a user designing and creating said software artifact via a computerized software engineering tool, said software artifact having common model elements, and said software artifact also having one or more model element automatons, wherein each of said model element automatons serves as a proxy for a real model element that varies between products within a product family; and using a fully automated computerized product actuator to provide a predefined feature profile that specifies the desired features for a variant of said software artifact to each of said model element automatons, thereby automatically instantiating real model elements in place of said model element automatons, to create said variant of said software artifact.