Ontologies play an instrument role in turning the current Web into a network of knowledge resources and services. Learning ontologies is not an end in itself. In addition to enabling the semantic Web, ontologies may facilitate searching and filtering relevant and trustable information on a subject matter in which a user is interested. As companies and organizations are shifting towards semantic Web services, ontologies become indispensable in expressing request profiles, service profiles, and process models. Ontology learning models may be wrapped as Web services. Service providers are motivated to describe new services and transform legacy services using established ontologies in order to increase the accessibility of their services to consumers. Third parties who are interested in providing add-on services will benefit from ontologies in integrating existing services. An individual who prefers personalized services and content delivery can specify their profiles with popular ontologies such as FOAF.