Scientific discovery related to software is based on a centuries-old paradigm common to all fields of science: setting up hypotheses and testing them through experiments. Repeatedly confirmed hypotheses become models that can describe and predict real-world phenomena. The best-known models in software engineering describe relationships between development processes, cost and schedule, defects, and numerous software "-ilities" such as reliability, maintainability, and availability. But, compared to other disciplines, the science of software is relatively new. It's not surprising that most software models have proponents and opponents among software engineers. This introduction to the special issue discusses the power of modeling, the promise of data repositories, and the workshop devoted to this topic.