Abstract: Client software, enabling a client to run a network based application which uses structured data, in which the client software comprises: (a) a communication layer to send and receive messages over the network; (b) a database layer to store, and allow querying of, the structured data; (c) a rendering layer which generates, from the structured data in the database layer, data for a user interface; wherein the client software is self-contained to provide all of the communications, data storage and rendering resources needed to run the network based application on the client device. The 3 Layer System is fully integrated and therefore requires no additional client side code to be written. Normally, this level of self-containment on the client side does not exist, so that a developer wishing to deploy a network based application to a client device needs to write client side custom code for the user interface.