Process XML Schema

Good morning ! I want to ask you about the XML file "processName.proc" ! In this file there is information about the whole process (tasks, contract, inputs, business data etc...), But there is no information about the variables used in the tasks associated, the ones we define in the UI Designer, is there any indication about those variables in the XML File that I couldn't pay attention to ?

If no, where Can I get information about those variables from a file ?