SysML v2 Reference Implementation — PlantUML Visual Design Analysis¶

Overview¶

The official SysML v2 Pilot Implementation (org.omg.sysml.plantuml) generates PlantUML text from parsed SysML v2 models using a Visitor pattern in Java. It does not modify PlantUML's source code. Instead, it maps SysML v2 concepts to the closest available PlantUML syntax, accepting visual approximations and relying on stereotypes/legends for semantic clarity.

1. Element Box Shapes: Usage vs Definition¶

The Distinction¶

In SysML v2, every structural element comes in two forms: - Definition (e.g., part def Wheel) — a classifier/type - Usage (e.g., part frontLeft : Wheel) — an instance/occurrence of a definition

How the Reference Implementation Renders Them¶

Both are rendered using PlantUML's rectangle keyword. The visual distinction is achieved through stereotypes, not different shapes:

rectangle "Wheel" as E1 <<(D,brown) part def>>
rectangle "frontLeft" as E2 <<(P,limegreen) part>>

Key mechanism: styleString(Type typ) in SysML2PlantUMLText.java

Determines the metaclass name from the EMF EClass (e.g., PartDefinition, PartUsage)
Strips Definition → adds def suffix; strips Usage → no suffix
Wraps in a stereotype with a colored icon letter:
(D,brown) for Definitions
(P,limegreen) for Parts (Usage)
(P,blue) for Ports
(B,green) for Items
(U,orange) for generic Usages
(B,lemonchiffon) for Behaviors
(F,yellow) for Features

Rounded Corners¶

The reference implementation uses PlantUML's skinparam roundcorner to give all boxes rounded corners uniformly. There is no distinction in corner radius between Usage and Definition — both get the same roundcorner value (typically 20).

skinparam roundcorner 20

Special Elements¶

Element	PlantUML Keyword	Stereotype
Actor (via `ActorMembership`)	`actor`	`<&person>` icon prefix
Stakeholder	`actor`	`<&people>` icon prefix
Package	`package`	none
Requirement	`rectangle`	`<<requirement>>`
State	`state`	state diagram mode
Action	`rectangle`	`<<action>>`

2. Relationship Arrow Approximations¶

The reference implementation maps SysML v2 relationships to PlantUML arrows via StyleRelDefaultSwitch in SysML2PlantUMLStyle.java. Each relationship type returns a specific arrow string.

Mapping Table¶

SysML v2 Relationship	PlantUML Arrow	Visual Result	Notes
OwningMembership	`+--`	solid line with `+`	Standard containment
Membership (non-owning)	`+..`	dotted line with `+`	Non-owning membership
FeatureMembership (composite)	`*--`	solid line with filled diamond	Composite aggregation
FeatureMembership (non-composite)	`o--`	solid line with hollow diamond	Shared aggregation
FeatureTyping	`--:\|>`	solid line with `:` and block arrow	UML realization-like
Redefinition	`--\|\|>`	solid line with double bar + block arrow	UML realization-like
Specialization (general)	`--\|>`	solid line with block arrow	UML generalization
BindingConnector	`-[thickness=5]-`	thick solid line (no arrowhead)	Emphasized connection
Connector (with metadata)	`-[thickness=3]->`	medium solid arrow	Connection with flow
Connector (no metadata)	`-[thickness=3]-`	medium solid line (no arrowhead)	Plain connection
Succession	`-->`	dotted arrow	Temporal ordering
Flow / FlowUsage	`-->`	dotted arrow	Item flow
SuccessionFlowUsage	`..>`	dotted arrow (short)	Flow in succession
Dependency	`..>>`	dotted double-arrow	UML dependency
AllocationUsage	`-[thickness=5,dotted]->`	thick dotted arrow	Allocation
Comment	`..`	dotted line (no arrowhead)	Annotation link
MetadataFeature	`..@`	dotted line with `@`	Metadata annotation
Import	`..>`	dotted arrow	Import relationship
SendActionUsage	`..>>`	dotted double-arrow	Message send
AcceptActionUsage	`<<..`	dotted double-arrow (reverse)	Message accept
SatisfyRequirementUsage	`-->`	dotted arrow	Satisfaction
PerformActionUsage	`-->`	dotted arrow	Performance
ExhibitStateUsage	`-->`	dotted arrow	Exhibition

What's Lost in Translation¶

SysML v2 Semantics	PlantUML Approximation	Gap
Redefinition (slash on arrowhead)	`--\|\|>` (double bar)	Different symbol entirely
Feature typing (`:\|>`)	`--:\|>`	Closest available, uses `:` prefix
Binding (no arrowhead, thick)	`-[thickness=5]-`	Good approximation
Flow (open arrowhead)	`-->` (filled arrowhead)	Arrowhead shape differs
Provided/Required interface	Not directly supported	Must use stereotypes

3. Redefinition Decoration on Features¶

When decoratedRedefined style is enabled, redefined features get inline decoration:

"featureName" as E1 <<(U,orange) feature>>
E1 :> redefinedFeatureName

The code in VStructure.java adds \n//:>>redefinedFeature// as a note inside the box, or uses the PlantUML icon <&bar-trig> prefix with the redefined name struck through:

<&bar-trig> featureName <s>redefinedFeatureName</s>

4. Compartment Rendering¶

The reference implementation supports compartments inside boxes for: - Attributes - Ports - Connections - Requirements - States - Actions

These are rendered as PlantUML compartment sections within rectangle or component blocks:

rectangle "Wheel" as E1 <<part def>> {
  attribute radius : LengthValue
  port hub : PortDefinition
}

5. Style System¶

The reference implementation defines three primary styles:

Standard B&W (`STDBW`)¶

skin sysmlbw
skinparam monochrome true
skinparam wrapWidth 300
hide circle

Standard Color (`STDCOLOR`)¶

skin sysmlc
skinparam wrapWidth 300
hide circle

Plus custom relationship styling: - Connectors: -[thickness=3,#blue]- - BindingConnector: -[thickness=5,#red]- - FeatureValue: -[thickness=5,#red]-

PlantUML Style (`PLANTUML`)¶

Uses standard PlantUML defaults with colored stereotypes.

Direction & Layout Options¶

TB — top to bottom direction
LR — left to right direction
POLYLINE — polyline line type
ORTHOLINE — orthogonal line type

6. Multiplicity¶

Multiplicity can be shown in three modes: - EDGE — on the relationship arrow (default) - NODE — inside the element box - BOTH — on both - NONE — hidden

Implicit multiplicities are hidden by default unless implicitMultiplicity is enabled.

7. Key Takeaways for Our Implementation¶

No PlantUML modification needed — the reference impl uses only standard PlantUML syntax
Stereotypes carry semantic weight — the colored (Letter,color) icons are the primary visual differentiator between element types
Arrow approximations are accepted — --||> for redefinition, --:|> for typing
Thickness + color differentiate relationships — binding is thick red, connectors are blue
Rounded corners are uniform — no shape difference between Usage and Definition
Compartments show internal structure — attributes, ports, etc. inside boxes
A legend is essential — without it, the approximations are ambiguous