MOMIS (Mediator envirOnment for Multiple Information Sources) is a framework for information extraction and integration of heterogeneous structured and semi-structured information sources. The result of the integration process is a Global Virtual View (in short GVV) which is a set of (global) classesthat represent the information contained in the sources being used. In this paper, we present the application of our integration concerning a specific type of source (i.e. web documents), and show how the result of the integration approach can be exploited to create a conceptualization of the domain belonging the sources, i.e. an ontology. Two new achievements of the MOMIS system are presented: the semi-automatic annotation of the GVV and the extension of a built-up ontology by the addition of another source.