arfgen reads in the pattern range from the DSS information in the spectrum dataset, and multiplies the quantum efficiency curve by the fraction of the events which fall in these patterns as a function of energy. If any problem is found with the PATTERN definition in the DSS; e.g. it is missing completely, it is unbounded or it is non-standard then the entire range of allowed patterns (0-31 for the MOS and 0-255 for the PN) are assumed. In these cases the warning NonStandardPatterns is issued. The standard ranges are singles (pattern 0 only), doubles (patterns 1-4 only), singles plus doubles (patterns 0-4) and for the MOS singles+doubles+triples+ quadruples (patterns 0-12). All other combinations are considered to be non-standard.