Nowadays models, rather than code, become the key artifacts of software development. Consequently, this raises the level of requirements for modeling languages on which modeling practitioners should rely in their work. A minor inconsistency of a modeling language metamodel may cause major problems in the language applications; thus with the model driven systems development the solidness of modeling languages metamodels becomes particularly important. At its current state the UML metamodel suggests a significant area for improvement. In this work we present an alternative metamodel that was inspired by RM-ODP standard and that solves the problems of UML. RM-ODP was mentioned in UML specifications as a framework that has already influenced UML. Our metamodel was formalized, thus its resulting models can be simulated and checked for consistency. So, our proposed solution carrying a constructive potential towards improvement of the UML metamodel, may have a real practical impact on the UML specifications.