Question: 1. What are the implications of schema evolution for existing data?
2. Systems typically support integrity constraints in a procedural fashion, via methods; the main exception is that referential constraints are typically supported (at least in part) declaratively. What are the advantages of procedural support? Why do you think referential constraints are handled differently?
3. R. G. G. Cattell and J. Skeen. "Object Operations Benchmark." ACM TODS 17, No. 1 (March 1992).