Abstract: An XML interpreter adapted to be loaded into a printer and executed by the printer. The XML interpreter receives, stores, navigates through and retrieves XML elements from an incoming data stream and calls a formatting program inside the printer and to allow the formatting program to perform rule-based formatting of the information carried by the XML structure. The XML interpreter has an XML parser for building a DOM tree; and an XPath processor comprising an XPath parser for parsing an XPath string into a data structure and an XPath interpreter which receives the data structure from the XPath parser and retrieves the data from the DOM tree.