In this volume, Steven Evans reports on a quarter century of work-work that resulted in a commercial product known as the PACE System. An advanced clinical management system, PACE links all care delivery set tings and reaches across multiple episodes. It offers capabilities critical to managed care, including care planning and clinical pathways, the critical pathway analyzer and clinical repository central to outcomes-based care, and more. The pages that follow describe the PACE project, focusing on its knowl edge base and semantic network. They offer insights into system implemen tation and address the synthesis of principles within the PACE System. From this project in nursing informatics, Steven Evans relates both suc cesses and failures, sharing the strategies and techniques to adopt and pitfalls to avoid in a project that followed five years of preliminary theo retical work. With clarity and candor, he gives us the benefit of two decades of project development, first in academia and then in the commercial sector. Over the course of the project, many tens of millions of dollars and close to 500 person-years of effort were invested. Building on the strong conceptual base developed at Creigton University's School of Nursing, the project has seen exponential growth in its clinical capabilities since entering the commercial sector in 1989.