Ontologies are the first step toward realizing the full power of online e-commerce. Ontologies enable machine-understandable semantics of data, and building this data infrastructure will enable completely new kinds of automated services. Software agents can search for products, form buyer and seller coalitions, negotiate about products, or help automatically configure products and services according to specified user requirements. The combination of machine-processable semantics of data based on ontologies and the development of many specialized reasoning services will bring the Web to its full power. The authors discuss: taxonomies; information sources; future issues; business viewpoints; the e-marketplace; and B2B e-commerce standardisation and integration.