1. A method of creating and executing an application on a wireless mobile device having an operating system and a virtual machine executed by said operating system, said virtual machine for interpreting application definition files defining applications in a markup language, said method comprising: at said mobile device: receiving an application definition file with metadata, said application definition file comprising said markup language and including: a format of a user interface for said application at said mobile device; a format of network messages for exchange of data generated by said application; and a format for storing data related to said application at said mobile device, said metadata including: a location at said mobile device for said application definition file; and a reference to an image file representing an icon to be displayed at said mobile device and whose selection shall initiate execution of said application; receiving said image file in association with said application definition file; creating an application descriptor file based on said metadata, said creating comprising: assigning, to a variable of said application descriptor file, said reference to said image file; and specifying in said application descriptor file said location at said mobile device for said application definition file; registering said application descriptor file with said operating system that is executing said virtual machine; at said operating system: responsive to said registering, presenting said icon based on said variable of said application descriptor file; receiving an indication of selection of said icon; indicating said selection to said virtual machine; at said virtual machine: responsive to said indicating, interpreting said application definition file to create an application; and executing said application, such that said virtual machine for executing said application is rendered transparent to a user of said mobile device.