Efficient processing of aggregation queries is essential for decision support applications. This paper describes a class of query transformations, called eager aggregation and laty aggregation, that allows a query optimizer to move group-by operations up and down the query tree. Eager aggregation partially pushes a groupby past a join. After a group-by is partially pushed down, we still need to...

Walking in to teach your first lecture as a newly minted assistant professor can be an intimidating experience. All eyes are on you, and the facial expressions of the students communicate emotions ranging from interest and excitement to boredom and sleepy disengagement. You know you want to hook your students on the class subject as soon as possible to encourage them to be more responsible for ...

The growing complexity of modern computer architectures increasingly complicates the prediction of the run-time behavior of software. For real-time systems, where a safe estimation of the program’s worst-case execution time is needed, time-predictable computer architectures promise to resolve this problem. The stack cache, for instance, allows the compiler to efficiently cache a program’s stack...

This paper presents JECho, a Java-based communication infrastructure for collaborative high performance applications. JECho implements a publish/subscribe communication paradigm, permitting distributed, concurrently executing sets of components to provide interactive service to collaborating end users via event channels. JECho’s efficient implementation enables it to move events at rates higher...