Audience member (commercial real-estate company) asks how to handle migrating data from decades-old legacy systems where the good domain signal is already lost. Garofolo: build the new model first, then map legacy data to it by emitting synthetic events like 'legacy foo imported' as the start of each new stream. A dedicated legacy event type lets you distinguish old from new data. The original domain events are gone — like a lossy compression — so you make the best of what you have while still getting pub/sub benefits.