XForms Space Invaders

John J. Chelsom

Seven Informatics Ltd.

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Preliminary Proceedings

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XForms Space Invaders

Balisage: The Markup Conference 2019
July 30 - August 2, 2019


The Model-View-Controller (MVC) paradigm is a design pattern for creating applications in which: the View (web page) interacts with the user; the Model controls manipulation of the data; and the Controller orchestrates the work of the view and the model. Implementing the classic arcade game Space Invaders in an XForms workbench proved to be a successful testbed for this approach. Key functionalities required for Space Invaders are an application “heartbeat” to control the speed/progression of the invaders; animated graphics for the invaders, the Mystery Ship, and laser fire; and the user-controlled laser cannon. The workbench was implemented using Orbeon Forms, an open source framework which supports XForms 1.1 with a number of custom extensions, including Javascript actions, Attribute Value Templates on XHTML elements, and listeners for “keypress” events. Most of the extensions required are included in the draft XForms 2.0 specification (albeit with slightly modified syntax).