This primitive data transfer API was designed so that more complete data transfer models could be built on top of it. Let's take a look at the clipboard model. The central feature of the model is the clipboard, which is basically a slot that holds a transferable object representing a single piece of data. The clipboard is shared among several clients. The transferable object represents the data, it is not the actual data.
Clients can put an object in the slot or they can get it from the slot.
Putting an object in the slot corresponds to copying to or cutting to the clipboard. Getting an object from the slot corresponds to pasting from the clipboard. One client at a time is designated as the clipboard owner. This is the client that last put an object in the slot. When another client gets the object from the slot and requests the data, the clipboard owner must provide the data.