ISO/IEC 18050:2006 specifies two methodologies for the measurement of specific print quality attributes of two-dimensional bar code symbols printed within the requirements of Digital Postage Marks. One of these methodologies is applicable to multi-row bar code symbologies and the other to two-dimensional matrix symbologies. ISO/IEC 18050:2006 defines methods for grading print quality attributes and deriving an overall assessment of symbol quality. In addition, it gives information on possible causes of deviation from optimum grades so as to assist users and postal operators in taking appropriate corrective action. ISO/IEC 18050:2006 applies only to those two-dimensional symbologies for which a reference decode algorithm has been defined, and provides an indicative read rate for limiting mean parameter values. The methodologies can be applied partially or wholly to other similar symbologies.