To deal with increasing complexity, volatility, and uncertainty, a process for engineering software-intensive systems in an open world, called Organic Aggregation Process (OAP), is proposed. It is based on a concept called “Organic Aggregation”, and consists of a coherent and flexible aggregation of carefully-categorised, hierarchically organised, and inter-connected activities. It supports flexible process aggregations via a capacity reuse mechanism called
. A model-driven method and a supporting tool environment are integrated into OAP, which enables efficient manipulation and utilisation of OAP models, and automatic generation of concrete systems. It supports, and promotes a focus on, high-level intellectual efforts such as perception of reality, rationalisation of problem situations, and derivation of “soft” desired ends. A proof-of-concept case study is briefly presented in this paper to illustrate the application of OAP approach in a real world setting.