It would be nice if C2 could read, and process, XML files. I am thinking of using XML files as a way to add new quests, items, opponents, etc... to a game that has been previously released as a way to expand the game.
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I think you could use the AJAX object in Construct 2 for that. AJAX can be used for interactive communication with an XML file. Here is a tutorial on how to do it with php:
AJAX Example with Construct 2
I don't know if that will help but I'm sure there are some AJAX/XML tutorials out there.