Due to the richness of the concrete syntax of both CASL and ELAN, it would be rather difficult to envision a direct translation. We preferred to implement a translation tool based on the underlying abstract syntaxes available for CASL and ELAN. These two abstract syntaxes are expressed by different instances of ATerms [BJKO99]. Therefore, the translation problem was also a good exercise for testing the ATerms library developed by the ASF+SDF group 2