How to Cheat at Tic-Tac-Toe With XML

I’ve spent a lot of time lately looking for and at XML authoring tools. Usually, it’s a pretty dry exercise, but I just came across one that made me laugh.

Xopus is an XML authoring tool that operates in the browser (IE 6 or 7 and Firefox 2 or 3). To illustrate the tool’s capabilities (and their sense of humor) the developers have a demo on their website in which you can author an XML document in such a way that it feels like you are playing tic-tac-toe against a computer. It’s awesome.


Here’s how it works. The developers wrote a schema that essentially describes the valid states of a tic-tac-toe game. When you click in a square, Xopus validates the document, and finding it “invalid”, responds (via javascript) by putting an X in another square. And so it goes until the game is over. There’s an XSL to render the game in the browser. It’s pretty neat. And the best part: if you find yourself about to lose a game of tic-tac-toe to an XSD schema (how embarassing!) you can cheat and Undo. I don’t know yet how useful Xopus will be to me for real work, but this is easily the most fun application of an XML authoring tool I’ve seen.