Optimizing Sequences of DB Operations Problem: Workflows, query generators, appl programmers all produce sequences of simple steps Op1 -> Op2 -> Op3… -> OpN Overhead on each call Sometimes expensive materialization of intermediate results Goal: Merge subsequences into more complex queries Op123 -> Op45… -> OpN When can you merge? How much should you merge?

Where to do what when in distributed query processing Problem: Data-intensive computations over distributed data Scientific and commercial examples Heterogeneous environments Want to spread the work over multiple systems, but Load on systems varies unpredictably Costs of shipping data may be prohibitive Limited use of and lack of mechanisms for function-shipping today Cost of evaluating more options may be prohibitive Goal: Enhance performance of distributed queries Respond to changing environment