Figure 28: Units in SysML

Gallery
Tutorial
TRAIL: SysPhS-1.1 specification body figures in MagicDraw SysML (or Cameo Systems Modeler) vs Modelica [using Wolfram SystemsModeler]
Section
Topic level
INTERMEDIATE
SysML keywords
ValueType
ValueType::unit
Unit
Real
Modelica keywords
Real
Keywords
Slide kind
SysML Block Definition Diagram (BDD)
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SysPhS-1.1: 'Data types in SysML are called value types.'
The above statement in SysPhS-1.1 is not quite accurate. Indeed:
SysML: Although not encouraged, you can still use a DataType to type a Property of a Block, it just won't be listed in the 'values' compartment. Prefer the SysML ValueType versions of primitives!
The main point is:
SysML-1.6: 'SysML defines ValueType as a stereotype of UML DataType to establish a more neutral term for system values that may never be given a concrete data representation.'
SysML-1.6: 'SysML ValueType adds an ability to carry a unit of measure and quantity kind associated with the value.'
SysPhS-1.1: 'SysML numeric value types can be linked to units, where units are modeled with the SysML Unit block. These units are linked to value types that are generalized by SysML’s numeric value types. Units and their symbols are from ISO 80000.'
SysPhS-1.1: 'Figure 28 shows how a value type with units is defined in SysML, from the units library in Figure 20 [ERROR], Subclause 11.2.2 [ERROR]. It has a value type Force that specializes the Real value type and has newton as unit. The newton unit has a symbol N.'
There's probably an error in the reference to Figure 20:
SysPhS-1.1: p.45: 10.11.2 SysML modeling: Reference to 'the units library in Figure 20, Subclause 11.2.2' is wrong
SysPhS-1.1: 'Modelica data types can be subtyped to add a unit symbol. The interpretation of this symbol is not defined in Modelica.'
SysPhS-1.1: 'The following Modelica code corresponds to Figure 28. It has a type Force, which extends Real, and the unit symbol N assigned to it.' 

type Force=Real(unit="N");
The ValueType Force won't export alone from the MagicDraw SysML Plugin, but we've already seen it used in context in models in previous slides, the export is identical: 

type Force=Real(unit="N");
Up next
Figure 29: State machine in SysML
Notes
[ASSERTION, OPTION]{INFORMATIVE} SysML: Although not encouraged, you can still use a DataType to type a Property of a Block, it just won't be listed in the 'values' compartment. Prefer the SysML ValueType versions of primitives!
[ISSUE] SysPhS-1.1: p.45: 10.11.2 SysML modeling: Reference to 'the units library in Figure 20, Subclause 11.2.2' is wrong
Snippets (quotes/extracts)
  [UML-2.5.1] DataTypes model Types whose instances are distinguished only by their value
  [SysML-1.6] SysML defines ValueType as a stereotype of UML DataType to establish a more neutral term for system values that may never be given a concrete data representation.
  [SysML-1.6] SysML ValueType adds an ability to carry a unit of measure and quantity kind associated with the value.
  [SysPhS-1.1] Data types in SysML are called value types.
  [SysPhS-1.1] SysML numeric value types can be linked to units, where units are modeled with the SysML Unit block. These units are linked to value types that are generalized by SysML’s numeric value types. Units and their symbols are from ISO 80000.
  [SysPhS-1.1] Figure 28 shows how a value type with units is defined in SysML, from the units library in Figure 20 [ERROR], Subclause 11.2.2 [ERROR]. It has a value type Force that specializes the Real value type and has newton as unit. The newton unit has a symbol N.
  [SysPhS-1.1] Modelica data types can be subtyped to add a unit symbol. The interpretation of this symbol is not defined in Modelica.
  [SysPhS-1.1] The following Modelica code corresponds to Figure 28. It has a type Force, which extends Real, and the unit symbol N assigned to it.
Visit also
SysPhS-1.1
SysPhS zone (SysML Extension for Physical Interaction and Signal Flow Simulation)
Figure 8-10: Model library for primitive value types
Visit also (backlinks)
Related slides (includes other tutorials)
Figure 8-14: Defining Value Types with units of measure from the International System of Units (SI)
Figure 8-18: Example of Unit, QuantityKind and ValueType definitions
Related slides (backlinks, includes other tutorials)