Software engineering today is heavily focused on the ideas of process maturity and continuous improvement. Processes are designed to deliver products. Process engineering should ideally rest on theoretical foundations of sound product engineering; however the field is currently lacking such foundations. Drawing inspiration from compiler design, we present a systematic framework for software product engineering that develops the product through successive levels of realization. The framework separates the concerns in software development by relating each level to a knowledge domain and localizing exactly on those qualities that become manifest in that knowledge domain. The basis of the framework is a mathematical model for reasoning about the correctness of realization schemes as well as the transformations between levels, so that each level preserves previously created qualities while adding new desired qualities. We also discuss some of the practical aspects of implementing this approach.