Composing Web

franca. However, they didn't address the fact that some QoS metrics, such as response time, depend on workload intensity level, which means a single value is not appropriate. The measurement process for each QoS metric should consider . what to measure (aggregates or percentiles); . how to measure (frequency, intervals, and tools); . who does the measuring (service providers or external independent agents); and . where the measurements are taken (Web service access point, network edge, or at the consumer). 5 A Web service's cost is often related to its quality. Faster, reliable, secure services will be more expensive, for example, but there could also be penalties associated with not meeting certain QoS goals or service-level agreements (SLAs). CompositeWeb Services Flow Figure 1 illustrates some Web service composition scenarios. Each service is represented with an oval and connected via directed arrows (an arrow from Web service A to Web service B indicates that A invoke