Yep, it is if you don't have any kind of documentation.
But the flags can help you (ACPI_WMI_METHOD, ACPI_WMI_EVENT).
A debug option was added to wmi.ko last month, the module will dump wmi informations on load, and it uses wmidump output format. So you don't have to search _WDG in your DSDT.
But even when you have found the correct UUID, you'll need to find/guess events code and methods id ...