The competitive market forces organizations to be agile and flexible so as to react robustly to complex events. Modeling helps managing this complexity. However, in order to model an enterprise, many stakeholders, with different expertise, must work together and take decisions. These decisions and their rationale are not always captured explicitly, in a standard, formal manner. The main problem is to persuade stakeholders to capture them. This article synthesizes an approach for capturing and using the rationale behind enterprise modeling decisions. The approach is implemented through a Domain Specific Modeling Language, defined as an extension of a standard Enterprise Architecture Modeling Language. It promotes coordination, enables presenting different stakeholders' points of view, facilities participation and collaboration in modeling activities - activities focused here on Enterprise Architecture viewpoints. To present its benefits, such as rapid prototyping, the approach is applied to large organizations in the context of Telecommunications service design. It is exemplified on modeling and capturing decisions on a conference service.