SYSML11 — 11. Activities

I suggest general policy for SysML: prefer Pins over ObjectNodes in all possible cases Use of ObjectNodes is problematic for many reasons, including: - In UML2.1.1 ObjectNode is abstract ! Tool vendors are thus forced to choose an arbitrary concrete placeholder (like <<CentralBufferNode>>, which is invalid). Use of Pins avoid this problem. - ObjectNodes are graphically less stable than Pins, as on has to manage the placement of ObjectNodes between Actions and two paths. - It is easier to trace type compatibility of connections between between Pins representing typed Parameters than across two paths via an ObjectNode with no binding to Parameters. - The placement of ObjectNodes on swimlanes boundaries (like in Figure B.35) is contrived and graphically unstable. Experience has shown that Pins are far easier to read, verify, and manage, and they correspond well to the idioms of signal processing known to engineers. I recommend that they be used in ALL SysML diagrams wherever possible, and that this be adopted as SysML policy, to the advantage of systems engineers, educators, and tool vendors alike.

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