Situational applications are typically short term applications that have to be developed with a limited programming effort by combining third-parties APIs. Recently, public Web sites offer an opportunity in this direction by providing large, ever growing, catalogues of Web APIs. Developers can select and integrate Web APIs to obtain, so called, mashup applications. Two relevant issues in this scenario are the selection of suitable Web APIs and producing programming code to integrate them. In this paper, we discuss how a semantics-enabled Web API registry can allow implementing proactive selection patterns for Web APIs to be integrated in a mashup and automatically generate in a guided way a programming code skeleton for the final application.