HOWTO use nested flowports within standard ports to model logical channels

Thu, 02/14/2008 - 16:37 — drkelly

MD SysML supports nested ports. One can sensibly combine nested SysML flowports and standard ports (UML Ports) to represent logical channels and information flow within a higher-order connection between standard ports and/or parts that is subject to a contract/protocol represented by an Interface.

This has no effect on the underlying metamodel or your project files, it is merely notational. Since a Port is a Property and a Property is a TypedElement, if the Type of Port also has Ports then they can be shown to nest. Although there are no notational examples of this in the UML2 or SysML specs (yet), it is completely consistent with the metamodels. So please DO feel free to use them whenever you like in MagicDraw UML and MD SysML !

The example here shows a simple system for monitoring the position and angle of a physical object with analog sensors, the output voltages of which are converted to a digital encoding that is acquired by a monitoring software application via a software API for polling an A/D card in a personal computer.

Please note that:

The physical flow of rotatation and position information is represented using connections between SysML flowports, as there is NO PROTOCOL and NO COMMAND set associated with the information flow.
There is no need here to specify what physical information is used here by these generic position and angle sensors to measure the rotation and position.
The analog voltage output from the sensors is modelled using connections between SysML flowports. Again, there is NO PROTOCOL and NO COMMAND set associated with the information flow.
There is no need to model the GND connection required for a voltage difference, the effective signals are being modelling, it is NOT a model of the electronic wiring.
The reusable A/D Card block has no notion at all about what is being measured, and thus the port names are quite general.
Nested flowports are used to represent the logical 'position' and 'angle' channels from the A/D API to the MonitorApplication !
The MonitorApplication uses specific names for ports to emphasise the known role when connected.

To see the defined Acquire and Poll interfaces of the standard ports please visit the associated BDD.

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