This is shown here in the structure compartment of WaterProcessingPlant on a BDD so we can see both black-box and white-box views, but it could also be shown in an IBD.

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Note how the 'itemProperty' on the ItemFlow on each Connector helps indicate the transformation of the H2O from dirty:Water through filtered:Water to steam:Steam then clean:Water.

The Connectors with the ItemFlows assigned have directional arrow indicators:

SysML-1.6: 'An ItemFlow describes the flow of items across a connector or an association. The notation of an item flow is a black arrowhead on the connector or association. The arrowhead is towards the target element.'

And the Ports with FlowPropert items on their defining Blocks also have nice direction indicators (at least when the name and label of the Port is not shown inside the Port rectangle):

SysML-1.6: 'Ports with types that have flow properties all in the same direction, either all in or all out, can have an arrow inside them indicating the direction of the properties with respect to the owning block.'

Some matters of style

The parts for :WaterFilter, :Boiler, and :Condensor are anonymous. There is only one of each, and their role is clear, so we can "Trust the Type":

Webel Best Practice: SysML: Webel: "Trust the Type!" - Often the name of the Type of an anonymous Property or instance-level element is completely sufficient to indicate its role - unless multiple Properties of the same Type have different roles within the same owner context!

Concise names 'i' and 'o' have been used on the Ports of the parts, because the names of the Types of their Ports in combination with the names of the Blocks of the parts are completely sufficient to describe their roles:

Webel Best Practice: Webel: If you must name your Ports or Pins, name them simply 'i', 'o', or 'io' (or 'oi') to indicate direction UNLESS you have to indicate a special role like 'iRole', 'oAuxiliary'. DO NOT use Port or Pin names like 'input', 'output', etc.

The explicit Port names iDirty:~F_Water and oClean:F_Water help describe the black-box view of the transformation performed by the WaterProcessingPlant. However, if the WaterProcessingPlant block had been instead been called DirtyWaterCleaningPlant the more concise port names 'i' and 'o' might also have sufficed.

We show next the same thing in an IBD but with more information exposed on the Port symbols.

Up next

WaterProcessingPlant - FlowProperty and ItemFlow example with Ports (in IBD with verbose Port compartments)

Notes

[NAMING, POLICY]{STRONG} Webel: For SysML Blocks and InterfaceBlocks used to type Ports with physical flows use 'F_UpperCamelCase' [may be combined with acronymn conventions]. The trailing part (after the underscore '_') may indicate the type that flows.

[POLICY] For Blocks and Interface blocks with one or more FlowProperty items, choose a direction convention and use it across one project.

[NAMING, POLICY, STYLE]{STRONG} SysML: Webel: "Trust the Type!" - Often the name of the Type of an anonymous Property or instance-level element is completely sufficient to indicate its role - unless multiple Properties of the same Type have different roles within the same owner context!

[CONVENTION, MODELLING, NAMING, TIP]{STRONG} Webel: If you must name your Ports or Pins, name them simply 'i', 'o', or 'io' (or 'oi') to indicate direction UNLESS you have to indicate a special role like 'iRole', 'oAuxiliary'. DO NOT use Port or Pin names like 'input', 'output', etc.

Snippets (quotes/extracts)

[SysML-1.6] A FlowProperty signifies a single flow element to/from a block. A flow property has the same notation as a Property only with a direction prefix (in | out | inout). Flow properties are listed in a compartment labeled flow properties.

[SysML-1.6] Item flows specify the things that flow between blocks and/or parts and across associations or connectors.

[SysML-1.6] FlowProperty::1_restricted_types A FlowProperty shall be typed by a ValueType, Block, or Signal.