We propose the development of a formal framework to unified metamodel within which models of class artefacts can be shared between different phases in a model-oriented environment. Model transformation approaches use different metamodels to represent source and target model of the system. This paper investigates for a unified metamodel when they share set of core representations in different phases and checks the possibilities for multidirectional transformation for code generation, upgradation and migration purposes. We envisage that the construction of an institutional framework for unified metamodel will not only increase the reusability of class artefacts but also provide a foundation for the consistent, independent and multidirectional transformation.