Relations

Relations connect classes, datatypes, and other relations.

External relations

External relations begin with the optional stereotype, then relation and the source end:

@mediation relation Enrollment [1] -- enrolls -- [1] Student

The general shape is:

@<stereotype> relation <Source> (<sourceEndMeta>)? <sourceCardinality>? <connector> <name>? -- <targetCardinality>? (<targetEndMeta>)? <Target>

For a named association, read the source first, then the connector, relation name, target cardinality, and target type:

kind Person
kind Course

@material relation Person [0..*] -- enrolledIn -- [0..*] Course

Internal relations

Internal relations are declared inside a class body. The enclosing class is the source:

kind University {
  @componentOf [1] <o>-- hasDepartments -- [1..*] Department
}

kind Department

Internal relations are useful when one element naturally owns the relation in the model text.

Connectors

Relation stereotypes

Tonto recognizes common OntoUML relation stereotypes:

material
derivation
comparative
mediation
characterization
externalDependence
componentOf
memberOf
subCollectionOf
subQuantityOf
instantiation
termination
participational
participation
historicalDependence
creation
manifestation
bringsAbout
triggers
composition
aggregation
inherence
value
formal
constitution

Custom identifiers and string stereotypes are also accepted by the grammar, but use standard stereotypes when possible so validators and generators can preserve meaning.

End names and end metadata

Relation ends can declare metadata and names:

kind Course {
  ({ ordered } primaryCourse) [1] -- hasSessions -- [1..*] ({ ordered } sessions) ClassSession
}

kind ClassSession

Supported end metadata:

ordered
const
derived
subsets <relationEnd>
redefines <relationEnd>

Example:

kind University {
  [1] <o>-- hasUnits -- [1..*] (organizationalUnits) OrganizationalUnit
  [1] <o>-- hasDepartments -- [1..*] ({ subsets organizationalUnits } departments) Department
}

kind OrganizationalUnit
kind Department specializes OrganizationalUnit

End metadata appears before the cardinality of the first end and after the cardinality of the second end. In the example, departments is a named target end that subsets the broader organizationalUnits target end.

Specialized and inverse relations

Relations can specialize another relation:

kind Person
kind Organization

@material relation Person [0..*] -- affiliatedWith -- [0..*] Organization
@material relation Person [0..*] -- employedBy -- [0..1] Organization specializes affiliatedWith

Relations can also declare an inverse:

@material relation Person [0..*] -- enrolledIn -- [0..*] Course inverseOf hasStudent
@material relation Course [0..*] -- hasStudent -- [0..*] Person inverseOf enrolledIn

Relator pattern

Use relators as truth-makers for material relations:

kind Person
kind Course

role Student specializes Person

relator Enrollment {
  enrolledOn: date [1] { const }
  @mediation [1] -- student -- [1] Student
  @mediation [1] -- course -- [1] Course
}

@material relation Student [0..*] -- enrolledIn -- [0..*] Course

This keeps the relation explicit and gives the model a place to attach attributes such as enrollment date or status.