Hi Azzedine,
probably it is not much effort - but I don't know the detail about AIDL. For Franca IDL to Android IDL, you could either use an EMF representation of AIDL (don't know if there is any) and create a transformation with Xtend. Or, you could just create AIDL text files from Franca models. For transformation from Android IDL to Franca IDL, it's probably most practical to use some AIDL parser and create the fidl text files from it. Can you tell us which direction is most relevant for you? Or maybe both?
Regarding the logical mapping of the concepts: It might be easy to map AIDL operations to/from Franca methods (incl. arguments and data types). But usually building such a mapping might be a challenge if you want to cover all the details. Probably someone knowing both IDLs should do some analysis and specifiy the mapping.
Hope this helps, regards,
Klaus