In this paper we study two echelon multi-server tandom queueing systems where customers arrive according to a poisson process with two different rates. The service rates at both echelons are independent of each other. The service times of customers is assumed to be completed in two stages. The service times at each stage are exponentially distributed. At the first stage, the customers may balk ...

Time of creation is one of the predominant (often implicit) clustering strategies found not only in Data Warehouse systems: line items are created together with their corresponding order, objects are created together with their subparts and so on. The newly created data is then appended to the existing data. We present a new join algorithm, called DiagJoin, which exploits time-of-creation clust...

Spatial joins are one of the most important operations for combining spatial objects of several relations. In this paper, spatial join processing is studied in detail for extended spatial objects in two-dimensional data space. We present an approach for spatial join processing that is based on three steps. First, a spatial join is performed on the minimum bounding rectangles of the objects retu...

Adaptive consistency is a solving algorithm for constraint networks. Its basic step is variable elimination: it takes a network as input, and produces an equivalent network with one less variable and one new constraint (the join of the variable bucket). This process is iterated until every variable is eliminated, and then all solutions can be computed without backtracking. A direct, naive imple...

We present a new algorithm for relational equi-join. The algorithm is a modification of merge join but promises superior performance for medium-size relations. In many cases, it even compares favorably with hybrid hash join.

In this study we present a technique for the parallel optimisation of join queries, that uses the offered coarse-grain parallelism of the underlying architecture in order to reduce the CPU-bound optimisation overhead. The optimisation technique performs an almost exhaustive search of the solution space for small join queries and gradually, as the number of joins increases, it diverges towards i...

We consider approximate join processing over data streams when memory limitations cause incoming tuples to overflow the available space, precluding exact processing. Selective eviction of tuples (loadshedding) is needed, but is challenging since data distributions and arrival rates are unknown a priori. Also, in many real-world applications such as for the stock market and sensor-data, differen...