The simplicity of the Web has drawbacks, including the difficulty of integrating information from multiple sources. Mashups may combine information from multiple sources in a custom integration, and user communities may collaborate to annotate images and videos. However it is desirable to integrate information by machine: this is the goal of the semantic web. "A major difficulty in realizing this goal is that most Web content is primarily intended for presentation to and consumption by human users; HTML markup is primarily concerned with layout, size, color, and other presentation issues"(59). Furthermore, "This vision of a semantic Web is extremely ambitious and would require solving many long-standing research problems in knowledge representation and reasoning, databases, computational linguistics, computer vision, and agent systems"(59). The paper discusses the use RDF and RDFS and OWL, (using some examples from the world of the Harry Potter stories). A brief description of ontologies and of the context of Description Logics are also given. It contains a discussion of reasoning systems as well as a Theoretical and practical relevance: Compares databases and OWL ontologies and gives a current computer science perspective on the semantic web. Lists some ontology applications such as specific reasoning systems and ontologies.