QuantityKind and ValueType example - length vs radius vs radius of tire

Gallery
Tutorial
TRAIL: Webel's ultimate guide to Systems Modeling Language (v1) with MagicDraw/Cameo
Section
08:03: The SysMLv1 QuantityKind and Unit
Topic level
ADVANCED
UML keywords
Generalization
ModelLibrary
SysML keywords
ValueType
QuantityKind
Unit
Unit::quantityKind
ValueType::quantityKind
Unit::definitionURI
QuantityKind::definitionURI
Unit::symbol
Unit::description
QuantityKind::symbol
QuantityKind::description
SimpleQuantityKind
SimpleUnit
SystemOfQuantities
Keywords
Slide kind
SysML Block Definition Diagram (BDD)
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The links typed by Associations are only shown to reveal some of the underlying QUDV machinery, you don't need those to create your own Units and ValueTypes.

The SimpleQuantityKind length from the QUVD ModelLibrary has the SimpleUnit metre. Another SimpleQuantityKind radius is linked to it, corresponding to an Association in the QUVD ModelLibrary that has one end 'general', which appears on the radius instance as a Slot assigned the value length (noting Generalization can't be used with instances).

Both length and radius are linked to the same SystemOfQuantities instance ISO 80000-3 Quantities.

Generalization can be used with ValueType to reuse and adapt radius. Why extend ? Here's just one possible reason:

You can use a ValueType to document how a value of a certain quantity kind should be measured (in a particular system, in a particular organisation, or according to an industry standard).
For example, one might document the pressure and seating of a tire for standard measurement of its outer radius.
Up next
QuantityKind and ValueType example - frequency vs clock frequency vs sound frequency
Notes
[TIP]{INFORMATIVE} QUDV in SysML refers to: Quantity, Unit, Dimension, Value. It is strongly influenced by the International Vocabulary of Metrology (VIM).
[TIP]{SUGGESTED} You can use a ValueType to document how a value of a certain quantity kind should be measured (in a particular system, in a particular organisation, or according to an industry standard).
[NAMING, POLICY]{STRICT} SysMLv1.x: ValueType naming: The Webel convention is 'UpperCamelCase' (a.k.a. PascalCase).
Snippets (quotes/extracts)
  [SysML-1.6] ... a SysML value property is understood to correspond to the VIM concept of "quantity" defined as a "property of a phenomenon, body or substance, where the property has a magnitude that can be expressed as a number and a reference" [VIM3-1.1].
  [SysML-1.6] A Unit is a quantity in terms of which the magnitudes of other quantities that have the same quantity kind can be stated.
  [SysML-1.6] Unit is defined as a non-abstract SysML Block defined in the SysML UnitAndQuantityKind model library.
  [SysML-1.6] Unit, or a specialization of it, classifies an InstanceSpecification to define a particular "measurement unit" in the sense of a "real scalar quantity, defined and adopted by convention, with which any other quantity of the same kind can be compared ...
  [SysML-1.6] QuantityKind is defined as a non-abstract SysML Block defined in the SysML UnitAndQuantityKind model library.
  [SysML-1.6] A QuantityKind is a kind of quantity that may be stated by means of defined units. For example, the quantity kind of length may be measured by units of meters, kilometers, or feet.
  [SysML-1.6] QuantityKind, or a specialization of it, classifies an InstanceSpecification to define a particular "kind-of-quantity" in the sense of an "aspect common to mutually comparable quantities" [VIM3-1.2], ...
  [SysML-1.6] quantityKind : InstanceSpecification [0..1] A kind of quantity, represented by an InstanceSpecification classified by a kind of SysML QuantityKind, that may be stated by means of units. A value type may optionally specify a quantity kind without any unit.
  [SysML-1.6] A DerivedUnit is a Unit that represents a measurement unit that is defined as a product of powers of one or more other measurement units.
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QuantityKind and ValueType example - frequency vs clock frequency vs sound frequency
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