Nowadays, modeling complex domains such those involving the description of human behaviors is still a challenge. An answer is to apply the Domain Specific Languages principle, which advocates that Domain Experts should model themselves their knowledge in order to avoid misunderstanding or loss of information during the knowledge elicitation phase. But Domain Experts must then be provided a modeling language enabling them to describe such complex domains. Moreover, in order to help them build models, immediate feedbacks would have to be available so that they can revise their modeling choices in earlier steps. Model execution is a way to address this issue. We provide xOWL, a language that can be used as a backend for multiple domain-specific syntaxes enabling Domain Experts to model themselves the structural as well as behavioral knowledge of their domain. xOWL comes with an interpreter integrated in an environment offering models executability in such way that Domain Experts can work in an iterative and incremental way using a trial and error approach. The implemented prototype is currently in use at EADS.