Metamodels: definitions of structures or ontological commitments?

The concept of metamodel is central in Model Driven Engineering (MDE). It is used to define the conceptual foundation of modeling languages. There exist specialized languages for specifying metamodels known as metalanguages. The most popular of them are object-oriented and support defining structures of the metamodels without considering the semantical underpinnings of the structures. In this paper we study the nature of metamodels from philosophical perspective. We claim that a metamodel is something more than an abstract syntax definition: it is an ontological commitment that guides the modeler in his perception about the real world phenomenon. Therefore, metalanguages should derive their foundation from the study of Ontology. We employ an ontological theory based on the Four-category ontology and the principles of metaphysical realism. We propose a metalanguage called OGML (Ontology Grounded Metalanguage) built upon the basic concepts of this ontology.