AbstractWe describe a method to migrate multiple instances of a successful single information system to a product line. The deployed product line is able to deal with the variants evolved over time in a cost‐effective manner. We proposed and used federated architectures that partition the software into so‐called genericity layers. We argue that federated architectures are at the heart of product lines, and we provide compelling arguments as to why federated architectures are a sound weapon in today's corporate strategy: they enable smooth enterprise integration and rapid change. We support our arguments with a real‐world case: we successfully migrated a large global transaction and settlement system with many site‐specific variations to a product line with a federated architecture. Moreover, we measured the success rate of this architectural modification effort by showing that the annual direct cost savings are of the order of millions of dollars during the deployment of the product line. Copyright © 2003 John Wiley & Sons, Ltd.