A method and system for comparing at least two structured data files. A computer polls at least one network device for data files. The computer determines a structural difference between a first data file and a second data file and creates at least one patch file based on the structural difference. The computer extracts at least one span from the at least one patch file, wherein the at least one span is defined by a starting point byte and a length measured in bytes and creates an ordered listing. The computer performs a lexer operation using the at least one span as a limiting criterion to limit an output of the lexer to statements that include the at least one span. The computer outputs the statements indicating changes in a configuration between said first and second data files.