This paper is about the extension of the SysML/KAOS requirements engineering method with domain models expressed as ontologies. More precisely, it concerns the translation of these ontologies into B System for system construction. The contributions of this paper are twofold. The first one is a formal semantics for the ontology modeling language. The second one is the formal definition of translation rules between ontologies and B system specifications in order to provide the structural part of the formal specification. These translation rules are modeled in Event-B. Their consistency and completeness are proved using Rodin. We show that they are structure preserving (two related elements within the source model remain related within the target model), by proving various isomorphisms between the ontology and the B System specification