legacy data(mapping to be done by xi (in xml format)) to sap using idoc .
I need to work in an object in which requirement is like , the source data is directly extracted from legacy and input file is made. now i need to create an interface program which will be used to create purchase req. in weekly basis. now according to functional specification xi team will map the source data in xml format and then through idoc data is to be pushed into sap. i am confused about the step by step senario from source data to final pr creation . please clarify if somebody had worked on this kind of situation.