Despite their quality, few TEL systems are actually adopted in educational institutions. These educational technologies have not always the necessary flexibility for use in real educational contexts that often requiring the rapid adaptations to new and often unexpected events (Cottier et al., 2008). Indeed, TEL environements should be designed as "open" in which the teacher himself is able to lead the adaptation and reengineering of learning system at an abstract level. In our work, we consider that opening of pedagogical scenario allows for the opening of TEL system. This article focuses on an approach based on the Domain-Specific Modeling and Model-driven Engineering for supporting practitioner teachers in their activities through the instructional design process. In order to verify our proposal we took Hop3x as experimentation field. Our objective is to open this TEL system for its users by providing them a user-friendly editor which allows the design and adaptation of learning sessions at a high-level of abstraction. We illustrate the development process of Hop3x's Domain-Specific Language and specific editor.