MOF and OCL are commonly used for metamodeling: MOF to model the domain structure, and OCL for the well-formedness rules. Thus, metamodelers have to master both formalisms and understand how to articulate them in order to build metamodels that accurately capture domain knowledge. A systematic empirical analysis of the conjunct use of MOF and OCL in existing metamodels could help metamodelers un- derstand how to use these formalisms. However, existing metamodels usually present anomalies that prevent automatic analysis without prior fixing. In particular, it often happens that both parts of the metamodel (MOF and OCL) are inconsistent. In this paper, we propose a process for analyzing metamodels and we report on the pre-processing phase we went through on 52 metamodels in order to get them ready for automatic empirical analysis.