Abstract: A software client (139) for executing an application on a mobile communications device, the software client (139) comprising: a receiver module (140) to receive a file containing mark up language to define the application; a parser (141) to parse the file in order to generate the application during run time to create a native application for the mobile communications device; a screen builder (142) to generate UI components for the native application by mapping procedures defined by the mark-up Language to native application programming interface (API) calls of the operating platform of the mobile communications device.