[antiRepublicrat]

To run an XML application using Firefox the additional costs of developing the software for installation on the server and the costs of server access, whether in money or performance, must be added.

The question is still openness. Could you modify Firefox to gain that capability? Definitely. Could you modify Windows or IE to gain capabilities they don't have? No.

[StJacques]

"The question is still openness. Could you modify Firefox to gain that capability? Definitely. Could you modify Windows or IE to gain capabilities they don't have? No."

Who cares if you can modify Firefox to add XML capabilities? Can you design an XML application for Firefox users across the globe, counting upon each of them to modify their browsers to run the app? No.