  The Python--elsA user interface of the elsA cfd (Computational Fluid
Dynamics) software has been developed to allow users to specify simulations
with confidence, through a global context of description objects grouped inside
scripts. The software main features are generated documentation, context
checking and completion, and helpful error management. Further developments
have used this foundation as a coupling framework, allowing (thanks to the
descriptive approach) the coupling of external algorithms with the cfd solver
in a simple and abstract way, leading to more success in complex simulations.
Along with the description of the technical part of the interface, we try to
gather the salient points pertaining to the psychological viewpoint of user
experience (ux). We point out the differences between user interfaces and pure
data management systems such as cgns.
