title: Evaluation of gwt.xml
body: <p>I'm new to GWT and trying to understand the role of gwt.xml. The documentation says that one can specify things like &lt;replace-with ... &gt; where you can specify different implementations based on, say, the current user agent. My question is: who evaluates these rules and when? What part of the execution stack deals with gwt.xml? Can the rules be modified runtime, by the way?</p>