An arbitrary string that uniquely identifies the Physical Element and serves as the Element's key. The Tag property can contain information such as asset tag or serial number data. The key for PhysicalElement is placed very high in the object hierarchy in order to independently identify the hardware/entity, regardless of physical placement in or on Cabinets, Adapters, etc. For example, a hotswappable or removeable component may be taken from its containing (scoping) Package and be temporarily unused. The object still continues to exist - and may even be inserted into a different scoping container. Therefore, the key for Physical Element is an arbitrary string and is defined independently of any placement or location-oriented hierarchy.