Comments

Because the notation in the

Because the notation in the upper right (so-called "elided pin notation") is so controversial, this figure has been reproduced here in its entirety be extraction from the OMG's UML2.3 spec.

As far as I know, not a single UML tool supports the elided pin notation properly; many confuse an 'object flow (edge)' with and 'object flow (arrow)', and many incorrectly use a CentralBufferNode as a concrete ObjectNode (as a diagramming convenience). So instead of having 2 Pins in the underlying model and one ObjectFlow between them, the tools have 2 ObjectFlows (one to a CentralBufferNode, and one from it), and the extra CentralBufferNode, instead of just a drawn object node symbol between 2 drawn object flow arrows !

Therefore, I strongly recommend that you always, at least when modelling data and object flows, use explicit Pins (and I contend this does not lead to clutter as often claimed), and use a single ObjectFlow between the explicit Pins. Completely avoid the elided Pin notation !