A marketplace is the place where the demands and offers of buyers and sellers participating in a business transaction may meet. Therefore, electronic marketplaces are virtual communities in which buyers may receive proposals from several suppliers and make the best choice. In the electronic commerce world, the comparison between different products is not possible due to the lack of common standards, used by the community, describing and classifying them. Therefore, B2B and B2C marketplaces have to reclassify products and goods according to different standardization models. In this paper, we propose a semi-automatic methodology, supported by a web service based framework, to define semantic mappings amongst different product classification schemas (e-commerce standards and catalogues) and we provide the ability to be able to search and navigate these mappings. The proposed methodology is shown over fragments of UNSPSC and ecl@ss standards and over a fragment of the eBay online catalogue.