Ontology engineering is gaining a lot of focus due to the rapid technological development including the emergence of semantic web technology. Applying the full potential of semantic web faces some obstacles as in how to link information from different data sources. Since relational databases are considered the main data repository up till now, thus integrating data from different relational sources into Semantic Web becomes the main focus of most of today’s work. In this book a new approach to solve the problem of integrating database schemas and ontology schemas is introduced where a precise conceptual correspondence between the database and ontology models is established. Database schemas in the proposed approach are modeled using Object role modeling (ORM) technique. ORM is a powerful technique in its expressivity where more than eighteen constraints can only be presented in it. In order to integrate data into Semantic Web, the associated ORM schemas are translated into equivalent ontologies using the web ontology language. The logical foundation of the ontology language (Description Logics) is represented in order to facilitate capturing the semantics of ORM schemas.