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.

Icon class
far fa-sticky-note
far fa-sticky-note
Note kind
Policy level
Specification keywords
UML keywords
SysMLv1.x keywords
Please note carefully first: Your choices for the type of a FlowProperty in SysML are restricted to ValueType, Block, or Signal:

You can use a structured ValueType, but any quantity properties within it typed by ValueTypes won't be able to display any units, because a ValueType symbol does not have a values compartment. In this case you should probably use a structured Block with value properties.

One reason modellers tend to go for ValueType first is that if you choose a Block and use it to type a part property to be used for an ItemFlow::itemProperty, that property will list in the parts compartment, although conceptually it is just a "packet". This tip can help there:

Signal is a nice initial choice if you want to distinguish purely digital signal flow (such as a sensed TemperatureReading) from the flow of quantities involved in physical interactions. Use of Signal is fine as a conveyed Classifier for basic InformationFlow style ItemFlows, however, it's not well suited to a finer grained ItemFlow::itemProperty.

Beware that:

If you are using SysML Extension for Physical Interaction and Signal Flow Simulation (SysPhS) for physical interactions you MUST use a Block:

Relates to
Related notes
Related notes (backlinks)
Related snippets (extracts)
Visit also
Visit also (backlinks)