Relationship

A Relationship is a Model Element that represents a semantic or structural connection among Model Elements together with meaning such as its kind, direction, participating ends, roles, and constraints. Its precise semantics are determined by a Relationship kind such as Association, Dependency, Generalization, or Realization.

In UML 2.5.1, Relationship is an abstract general concept for relations among Model Elements. Association, Dependency, Generalization, and Realization are concrete Relationships with different semantics. SimpleModeling preserves these distinctions and does not reduce every connection to an Association.

The ordinary word relationship can describe a broad connection among people, events, documents, or other things. The modeling Relationship defined here is an identifiable Model Element with a specific Relationship kind and semantics. Ordinary prose uses of relationship are not references to this term.

Relationship primarily expresses structure and meaning on the Object side. Functional-side connections such as composability, parameter/result Type correspondence, and effect propagation are distinguished as appropriate Type or function relations.

CML (Cozy Modeling Language) describes the most specific applicable Relationship kind. Connecting two elements alone does not determine semantics, so distinctions among Association, Aggregation, Composition, Dependency, Generalization, and related kinds are preserved.

Scala fields, inheritance, trait mix-ins, Type bounds, and function parameters may realize different modeling Relationships, but syntax alone does not always uniquely recover the domain Relationship kind.

simplemodeling-lib Types and structures may realize modeling Relationships, but a library reference or containment alone does not determine Relationship semantics. The canonical model Relationship and its CML declaration remain the semantic basis.

Japanese articles and videos introduce the concept as モデル関係（Relationship） and shorten it to 関係 only while the modeling context remains unambiguous. Ordinary uses of 関係 are not automatically linked. When the concrete kind is known, a specific term such as Association, Aggregation, or Composition is used instead of only the general Relationship label.

SimpleModeling does not treat a Relationship as merely a drawn line; it makes the Relationship’s meaning, responsibility ownership, Multiplicity, and validity conditions explicit.