To support the transformation of system engineering from the project-based development of highly customer-specific solutions to the reuse and customization of ¡®system products¡¯, we integrate a process reference model for reuse- and product-oriented industrial engineering and a process reference model extending ISO/IEC 12207 on software life cycle processes with software- and system-level product management. We synthesize the key process elements of both models to enhance ISO/IEC 15288 on system life cycle processes with product- and reuse-oriented engineering and product management practices as an integrated framework for process assessment and improvement in contexts where systems are developed and evolved as products.