SysML+SysPhS: Flows: If you intend to use a Classifier to type the itemProperty of an ItemFlow on a Connector for a physical interaction you MUST use a Block (not a ValueType or Signal) so your can extend ConservedQuantityKind.

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Note kind
ASSERTION
MODELLING
TIP
Policy level
STRICT
Specification keywords
SysML-1.6
SysML-1.7
SysPhS-1.1
UML keywords
Signal
InformationFlow
InformationFlow::conveyed
SysMLv1.x keywords
Block
ValueType
ItemFlow
ItemFlow::itemProperty
SysPhS Keywords
ConservedQuantityKind
Keywords
Compare with the discussion of the more general options for general SysML modelling under:
Webel Best Practice: SysML: Whether you use a Block, ValueType, or Signal to represent something that flows (and can be applied to an ItemFlow) depends on what you want to achieve. If you want to indicate something structured with value properties with Units use a Block.
Relates to
Overview of flowing quantities and Port types with flows
Related notes
[MODELLING, TIP]{SUGGESTED} SysML-1.6/1.7: You can introduce a custom (user-defined) stereotype keyword «item» to indicate Properties that are to be used as "packets" for ItemFlows on Connectors. (SysMLv2 will have a formal way of treating such items/packets.)
[MODELLING, OPTION, TIP]{INFORMATIVE} SysML: Flows: If you use a Signal to type the itemProperty of an ItemFlow on a Connector, care must be take in how you create the Property or you might get an unwanted signal Reception on the owning context Block.
[MODELLING, OPTION, TIP]{INFORMATIVE} SysML: Whether you use a Block, ValueType, or Signal to represent something that flows (and can be applied to an ItemFlow) depends on what you want to achieve. If you want to indicate something structured with value properties with Units use a Block.
[PROPOSAL]{SUGGESTED} WISHLIST: Webel has suggested that future SysML should support the display of Classifier-level :features in compartments on a rectangular itemProperty symbol on an ItemFlow on a Connector in an IBD.
Related notes (backlinks)
Related snippets (extracts)
  [SysML-1.6] Item flows on connectors shall be compatible with flow properties of the blocks usages at each end of the connector, if any. The direction of the item flow shall be compatible with the direction of flow specified by the flow properties.
  [SysML-1.6] FlowProperty::1_restricted_types A FlowProperty shall be typed by a ValueType, Block, or Signal.
Visit also
SysPhS zone (SysML Extension for Physical Interaction and Signal Flow Simulation)
Visit also (backlinks)