In the last years, Instructional Design has seen the development of visual notation systems for supporting and enhancing the design process. Some of them concern the definition of learning goals, while others address the definition of learning activities or learning materials. These tools supposedly reduce the cognitive load and enhance design communication. Few contributions try to assess the impact that such models have on the practice of Instructional Design. This article introduces a general framework for evaluation, indicating key issues and providing guidelines for the design of an evaluation program. As an example, an implementation of the framework along with the data collected about E[2]ML is presented.