Empirically learned characteristics of a business process, like branching probabilities and average execution durations of activities, are usually used for process simulation and the creation of scheduling scenarios as a basis for process optimization. This information can also be utilized to calculate a probabilistic timed process model, based on the process structure. It yields time histograms which represent the probability for expected process executionduration and activity execution-intervals. In order to cope with the interoperability aspect of business processes these workflow-based concepts must be mapped on composite web service (CWS) environments. Slow autonomous web services, invoked by a CWS, can have a disastrous impact on the overall process response time. Thus techniques are needed predict the process duration based on the anticipated response time of participating web services, which enables us too avoid these services or to optimize them for faster execution.