I think right now, there has to be exact matches in the path structures between two input variables in order the data to be matched and processed. I agree that your example should be possible. Currently all the data matching algorithms are still based on a "flat world" that doesn't know about trees. Once you add tree structure into data mapping, I think you get a ton of new possibilities, your example being just one. I'd certainly welcome some new, tree specific, data matching schemes.