PCKS is a novel approach for systematically benchmarking semantic flow processing systems. Based on identifying the properties and challenges of a semantic flow processing system and data set at hand, we elaborate the importance of defining appropriate key performance indicators. In the corresponding paper published at ESWC 2013 we investigate how current benchmarks perform under PCKS. We find that their most significant shortcoming is their restriction to input throughput as the sole key performance indicator. Showing that semantic flow processing systems must be evaluated under other key performance indicators such as correctness. In our study we indicate how extend current benchmarks to systematically stress-test semantic flow processing engines. PCKS will help learning more about their performance under various evaluation criteria.