The PackML object model is composed of a series of tags. These tags can be one of three general type of tags Command Tags, Status Tags and Administrative Tags.
Command tags allow interaction with the state machine and general functionality of the server. Command tags include changing units, changing state machines. For additional detail see ISA-TR88.00.02-2015. In OPC UA command tags are generally mapped to Methods.
Status tags provide information about the state of the machine or device. This includes feedback from the commands issued and the general status. For additional detail see ISA-TR88.00.02-2015.
Admin tags provide information about alarming in the machines or device. This include Alarm history and some summary statistics about the machine or device. For additional detail see ISA-TR88.00.02-2015.