Structured vs Primitive DataType

Gallery

Tutorial

TRAIL: Webel's ultimate guide to Systems Modeling Language (v1) with MagicDraw/Cameo

Section

08:02: The SysML ValueType, Unit, and using values

Tags and keywords

Topic level

ESSENTIAL

UML keywords

DataType

PrimitiveType

SysML keywords

Slide kind

UML-2.5.1: 'DataTypes model Types whose instances are distinguished only by their value'

The slide is adapted from UML-2.5.1 Figure 10.3 DataType Notation:

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The Dependency relationships in this diagram are for illustration only

In general, a DataType may have substructure:

UML-2.5.1: 'If a DataType has attributes (i.e., Properties owned by it and in its namespace) it is called a structured DataType. Instances of a structured DataType contain attribute values matching its attributes. Instances of a structured DataType are considered to be equal if and only if the structure is the same and the values of the corresponding attributes are equal.'

But a PrimitiveType (a special kind of DataType in UML) does not have substructure:

UML-2.5.1: 'A PrimitiveType defines a predefined DataType, without any substructure. A PrimitiveType may have algebra and operations defined outside of UML, for example, mathematically.'

On a subtle note:

The SysML Complex "primitive" ValueType does in fact have substructure: realPart:Real and imaginaryPart:Real

Up next

SysML Complex ValueType

Notes

[TIP]{STRONG} In SysML, unless you MUST use a DataType or PrimitiveType from an existing ModelLibrary or Profile, you SHOULD probably be using a ValueType, Enumeration ValueType, or SysML PrimitiveValueType instead so that it integrates with the value system of SysML.

[CAVEAT] The SysML Complex "primitive" ValueType does in fact have substructure: realPart:Real and imaginaryPart:Real

Snippets (quotes/extracts)

[UML-2.5.1] DataTypes model Types whose instances are distinguished only by their value

[UML-2.5.1] A PrimitiveType defines a predefined DataType, without any substructure. A PrimitiveType may have algebra and operations defined outside of UML, for example, mathematically.

[SysML-1.6] Value types may be used to type properties, operation parameters, or potentially other elements within SysML.

[SysML-1.6] Although SysML indirectly imports the UML 2 PrimitiveTypes library ... due to the transitivity of package import, SysML provides a PrimitiveValueTypes model library that systems engineers can extend via SysML’s ValueType stereotype.

[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.

[UML-2.5.1] Features represent structural and behavioral characteristics of Classifiers.

[SysML-1.6] A SysML ValueType may define its own properties and/or operations, just as for a UML DataType.

[UML-2.5.1] A DataType is a kind of Classifier. DataType differs from Class in that instances of a DataType are identified only by their value. All instances of a DataType with the same value are considered to be equal instances.

[UML-2.5.1] If a DataType has attributes (i.e., Properties owned by it and in its namespace) it is called a structured DataType. Instances of a structured DataType contain attribute values matching its attributes.

[UML-2.5.1] Instances of a structured DataType are considered to be equal if and only if the structure is the same and the values of the corresponding attributes are equal.

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Figure 8-4: Abstract syntax extensions for SysML value types

Figure 8-10: Model library for primitive value types

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