1. A method for preparing data flow information regarding a data flow using at least one external data file, each of said external data files comprising columns of information, said method comprising: storing a data flow model, said data flow model comprising use data describing, for each of said at least one external data file, a use of at least one column from said external data file; storing metadata comprising data describing at least one column of each of said at least one external data file; and using said stored metadata to determine whether said data flow model and said external data files are consistent.