In this paper we present a framework for the evaluation and (re)design of modeling languages. We focus here on the evaluation of the suitability of a language to model a set or real-world phenomena in a given domain. In our approach, this property can be systematically evaluated by comparing the level of homomorphism between a concrete representation of the worldview underlying the language (captured in a metamodel of the language), with an explicit and formal representation of a conceptualization of that domain (a reference ontology). The framework proposed comprises a number of properties that must be reinforced for an isomorphism to take place between these two entities. In order to illustrate the approach proposed, we evaluate and extend a fragment of the UML static metamodel for the purpose of conceptual modeling, by comparing it with an excerpt of a philosophically and cognitive well-founded reference ontology.