This exploratory research investigates the evaluation process of conceptual specifications developed using either Extended Entity-Relationship (EER) or Unified Modeling Language (UML) conceptual models. In this paper, we provide a comprehensive framework for evaluating EER and UML conceptual schemas. Furthermore, we define classes of metrics facilitating the evaluation process and leading to the choice of the appropriate representation among several schemas describing the same reality. Based on quality criteria proposed in the literature, we select a subset of criteria relevant to conceptual EER schema quality evaluation. For each criterion we define one or several metrics allowing the designer to measure the schema quality. We evaluate alternative EER conceptual schemas representing the same universe of discourse using the appropriate criteria and their associated metrics. Finally, we extrapolate this evaluation process to UML schemas. Following the development of our framework, we analyze a case study and provide evidence in the support of the usefulness of the framework.