Just a point worth mentioning - I've been looking at a lot of device XML files lately that some folks say they just can't get to work, and I noticed a very common error that is probably worth mentioning:
You MUST have a <messageid> variable defined in your HEADER tags. The UDS console, and consequently enVision, will not be able to process your device XML if there is no messageid variable defined.
The MESSAGE tags must then contain an id2 parameter that defines the string from the log/event that matches where the <messageid> variable was set in the HEADER.
Please review this critical concept from your UDS course materials if you need more detail!