The algorithms for all the relational operators are written as if they were to be run on a single processor. As shown in Figure 3, the input to an Operator Process is a stream of tuples and the output is a stream of tuples that is demultiplexed through a structure we term a split table. Once the process begins execution, it continuously reads tuples from its input stream, operates on each tuple, and uses a split table to route the resulting tuple to the process indicated in the split table. 4 When the process detects the end of its input stream, it first closes the output.
