Relational DataBase Systems (RDBSs) are well-known and widely used in many organizations, however, semantic conflicts between the participating RDBSs must be resolved before data can be exchanged between them. Semantic resolution between the RDBSs is extremely difficult to address mainly because participating RDBSs are designed and built independently. Furthermore, individual RDBSs are likely to evolve over time and the changes must be reconciled dynamically. In this paper, we describe an approach to resolve the semantic conflicts between RDBSs automatically while allowing the individual RDBSs to evolve. Relational DataBase Ontology (RDBO) is created and used to ensure the semantic descriptions of the individual RDBSs are conformed to a set of vocabularies, structures, and restrictions. We show how a modified reasoning engine is used to validate and infer additional semantic relationships from the existing relationships. We also show how terms defined in different database ontologies are compared to each other semantically using semantic weights and our modified reasoning engine. As a result, RDBSs can interoperate with each other seamlessly and at the correct level of semantics defined in their ontologies.