A difficult point concerns the choice of the development language. If the language is close to the implementation procedure the prototyping process might be long. Developing with Smalltalk provides the facility to obtain a prototype in a reasonable time. The effort of adapting the prototype to a more efficient final version remains to the industrial partners. In addition to the development language is the problem of storage organization. Initially stored in Smalltalk files the knowledge bases were progressively redesigned for relational databases using Access.