Current conceptual models and methodologies for Web applications concentrate on content, navigation, and service modeling. Although some of them are meant to address semantic web applications too, they do not fully exploit the whole potential deriving from interaction with ontological data sources and and from Semantic annotations. This paper proposes an extension to Web application conceptual models toward Semantic Web. We devise an extension of the WebML modeling framework that fulfills most of the design requirements emerging for the new area of Semantic Web. We generalize the development process to cover Semantic Web and we devise a set of new primitives for ontology importing and querying. Finally, an implementation prototype of the proposed concepts is proposed within the commercial tool WebRatio.