A major aim of the Web service platform is the integration of existing software and information systems. Data integration is a central aspect in this con- text. Traditional techniques for information and data transformation are, however, not sucient to provide exible and automatable data integration solutions for Web and Cloud service-enabled information systems. The diculties arise from a high degree of complexity in data structures in many applications and from the additional problem of heterogenity of data representation in applications that often cross organisational boundaries. We present an integration technique that embeds a declarative data transformation technique based on semantic data models as a mediator service into a Web service-oriented information system architecture. Automation through consistency-oriented semantic data models and exibility through modular declarative data transformations are the key enablers of the approach. Automation is needed to enable dynamic integration and composition. Modiability is another aim here that benets from consistency and modularity.