Performance Functions for QoS Prediction in Web Service Composites

We contribute performance functions to model the quality of service (QoS) of web services in horizontal composites. Performance functions are thereby used to formalize service level agreements (SLAs) to enable automated verification. Inter-Component rating is a model for gathering additional QoS information from web services that rate the output of their predecessor web services in composites. Furthermore, we contribute two approaches to verify if a web service adheres to its claimed QoS described with a performance function. For this verification, claimed performance is compared with reading points gathered from spot-testing the quality of the web service. The first approach we discuss is function interpolation, the second one applies methods from computational trust. The paper also discusses the advantages and drawbacks of both approaches as well as the influence of measuring errors.