Try as we might, we make mistakes. Or change our minds. Sometime later, we decide against the new lookfeel changes and want to go back to the original. We don't want to re-edit the whole module again, because we've already got that old revision in the lib. We also do not want other applications that use this module to be affected - they should still use the new look and feel.

Now we've made several changes to lookfeel over time, and we don't remember exactly what revision number we want. We only know that we want to "fall back" to the code as it was on Dec. 3 - after our first rev but before the second.

We can accomplish this with another argument to the <USES> directive in our script, the DATE argument:

  <USES DATE="1999-12-03" lookfeel>

This tells Vortex to use the version of lookfeel available on Dec. 3, instead of the latest revision. If we make this change to example and reloaded it, then we see the old look and feel (white background).

Furthermore, the example application is now "frozen" in time: if someone makes yet another revision to lookfeel , our example will not see the new revision, because we're locked to the Dec. 3 rev level. All with less than a one-line edit.