The invention provides methods and apparatus, for interfacing communicating between a plurality of portable devices and a warehouse management system, each of the devices being equipped with a web browser for displaying visual content, the warehouse management system comprising for each of the devices an XSL file associated therewith, the XSL file comprising information for transforming XML data in a format which can be displayed on the web browser of the associated device, the method comprising: receiving, from the warehouse management system, a GUI screen comprising content to be displayed on the web browser of one selected device of the portable devices; generating XML data which describes GUI screen controls representing the content; transforming the XML data by use of the XSL file which is associated with the selected device; and transmitting the transformed file to the device for display by the device web browser.