There are two answers I can think of off the top of my head:
- you need to change the kind of alert to "Group" instead of "node". That's the dropdown at the top of the alert trigger tag (in the Win32 utility) or the top of the triggers page in the web-based alerting.
- don't use groups. Use a custom property which is actually more flexible in terms of what you can do with it (reports, alerts, display, etc).
Let me know if you need more details.
not sure if others are doing this better then this approach but I make my groups by dynamic queries. I add a node custom Property for something like system then run the dynamic query based on node.system begins with [enter your text here]
GO back and add the system value to your nodes you want. Now they will be added to the group.
NExt update your alerts to include node.system is [your text]