PartUsage

Original XMI declaration. §7.11 Parts, printed 58 / PDF 90; §8.3.11.3 PartUsage, printed 289 / PDF 321

What to understand

• A referential part remains a PartUsage. It is not converted into the metaclass ReferenceUsage just because its declaration contains ref.
• Owning a part declaration, featuring its values, and making those values composite are separate mechanisms.
• The declared partDefinition property has multiplicity 0..*. Class-level constraints still require at least one applicable PartDefinition typing; declaration cardinality alone is not the whole rule.
• The normalized defaults below describe metamodel fields. The multiplicity and composition of a part in a user model follow contextual SysML rules.

Graphical notation

These are representative, source-checked variants, not an exhaustive notation grammar. The illustrations are original redraws, not official figures.

Composite and referential part usages

Context: Usage nodes in structural views.

Rounded rectangle with a part usage label. The referential variant has a dashed outline and the ref prefix. Compartments and side ports are additional variants.

§8.2.3.11 Parts, printed 209 / PDF 241

Relationships and composition

Typing: PartDefinition

A part usage has applicable part-definition typing, explicit or supplied through its semantic specialization.

Condition: Do not restrict every allowed explicit type to PartDefinition; the source also permits qualifying item definitions and kernel structures.

§7.11.2, printed 61 / PDF 93

Nested declaration: PartUsage

A part usage can declare nested part usages as features in its context.

Condition: Permitted examples do not establish that every nesting is valid; membership, featuring and composition constraints still apply.

§7.6.3, printed 41 / PDF 73

Nested port: PortUsage

Ports can be declared within a part usage or its defining type.

Condition: The port typing and context-specific referentiality rules apply independently of the enclosing part.

§7.12.2–3, printed 63 / PDF 95

Connected example

wheel is a composite part usage within Assembly. spare is an owned but referential part usage. Both are typed by Wheel; the [0..1] on spare explicitly constrains its modeled values.

// Original documentation example. Source-reviewed; not parser-validated.
package AssemblyExample {
    port def Mount;

    part def Wheel {
        port hub : Mount;
    }

    part def Axle {
        port mount : Mount;
    }

    part def Assembly {
        part wheel : Wheel;
        part axle : Axle;
        ref part spare : Wheel[0..1];
        connection link connect axle.mount to wheel.hub;
    }

    part assembly : Assembly;
}

Verification: source-reviewed, not parser-validated or executed. §7.6.3 Usages, printed 40 / PDF 72; §7.11.2 Part Definitions and Usages, printed 61 / PDF 93

Properties

The explicit-redefinition view contains 113 active declarations, retaining declaration origins and excluding 3 replaced declarations. It deduplicates diamond paths by identity, excludes private inherited fields, and reports unresolved same-name collisions instead of choosing a winner.

These are metamodel property cardinalities and declared defaults. They do not determine the multiplicity or runtime values of a part, port or connection in a user model. Derived values still require their derivation rules. See property rules.

Replaced declarations

• KerML::Core::Features::Feature::isVariable → SysML::Systems::DefinitionAndUsage::Usage::mayTimeVary
• KerML::Core::Features::Feature::type → SysML::Systems::Occurrences::OccurrenceUsage::occurrenceDefinition
• SysML::Systems::DefinitionAndUsage::Usage::definition → SysML::Systems::Occurrences::OccurrenceUsage::occurrenceDefinition

Reconciliation and limits

Seed reconciliation: SelectedFieldsMatch for direct bases, declared property names/types/bounds/derivation/ordering/subsets/redefinitions, constraint names. This checks selected structural fields only; it does not approve the entire seed or all semantics.

• The examples have been checked against source notation, but no SysML parser or semantic engine was run.
• No exhaustive permission matrix or complete notation grammar is claimed.
• Effective property resolution covers explicit inheritance and redefinition identities; it does not evaluate constraint consistency, OCL derivations or executable behavior.

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