s exhibits diversity in the real world, mental abstraction world, document world, and machine world. Studying mappings between different forms of semantics helps unveil the uniformity in the diversity. This article investigates the mappings between three typical semantic models: the Web ontology language (OWL), relational database model, and resource space model (a classification-based semantic model). By establishing mappings between the semantic primitives of the three models, we study the mapping from OWL description onto resource space and analyze the normal forms of the generated resource space. Mapping back from resource space onto OWL description is then discussed. Further, we investigate the mapping between OWL description and relational database, as well as the mapping between relational database and resource space. Normal forms of the generated relational tables are analyzed. To support advanced applications on the future Web, we suggest integrating the resource space, OWL, a...