Delivering data and formatting information includes delivering object definition files from a server to a client; generating definitions and object instantiations at a client using JavaScript or another simple browser-interpreted language, for objects relating to data modeling and presentation; and presenting data using those objects at the client, using a web browser without a separate runtime environment or application plug-in, but maintaining substantial state at the web browser regarding the data itself and the format for its presentation. Definition files are modified to provide object properties consistent with a full object-oriented language, including for example hierarchical inheritance of object properties. Code ballooning generates definitions and individual instantiations, with the effect that a very large amount of DHTML, or another markup or presentation definition language for use with the application, can be generated from relatively small aggregate size of definition files communicated from the server to the client.