The TAG does have to be added manually, however if you add one to an object you can then right click and select multiple then select all of the other items to be tagged which is only 7 clicks I think, so in a building with a large number of Air tetminals you only need to tag one, then it will tag the rest of them with 4 more mouse clicks, if set up correctly the data can be very automatic with Auto-increment numbers and property sets attached to the style.
I dont think you can add the TAG to the MvPart, but then it does allow you to select different tags for different situations.
You can then also use the property set information for schedules.
Drew