An XML processing system for use in a barcode printer apparatus includes a computer system operatively coupled to the barcode printer apparatus. The computer system further includes an XML processor configured to receive, parse, and process an XML input data stream and obtain schema identified in the XML data stream from a schema repository. Alternatively, the system includes a SAX processor configured to receive and process the XML input data stream, a ZPL processor configured to receive and process a format template, a variable data integrator configured to develop an association between the XML data contained in the XML input data stream and the format template, a formatting engine configured to format the associated XML data according to a format governed by the format template, and a barcode rendering engine configured to receive the associated and formatted XML data and generate a bit map representative of the bar code label.