Computer-based learning aims in essence to imitate cognitive behaviors, assist learners and teachers in pedagogical exchanges and monitor their overall cooperation based on learning paradigms. In this respect, this paper is concerned with Problem-Based Learning (PBL). Designing PBL platforms comes up against the lack of reusable domain-specific or educational software assets. TO avoid such a problem, metamodeling (via a UML profile) is considered in this paper as a reliable way for instantiating PBL situation models. A semantics and a notation are in particular associated with the proposed metamodel in order to provide rigor but also flexibility in pedagogical scenario elaboration. An example in particular illustrates the applicability of the offered Educational Modeling Language (EML).