modicio/modic.io.model/Composition

Composition

@Entity
class Composition(var dataID: Long? = null, val uri: String = "", val role: String = "", val target: String = "", var isPublic: Boolean = false, var node: Node? = null)

A Composition is a stronger specialization of an AssociationRelation, i.e., it is a part-of relationship. To realize this binding strength, Compositions follow particular principles:

  • A Composition starts from a Node "A" and targets a Node "B". The composition relation is unidirectional and owned by Node "A". It means "B's" can be part of "A".

  • In this case, "A" and "B" must be part of the same Model.

  • Composition loops are forbidden and invalidate the Model.

  • Compositions can be private or public. The instance objects of a public composite element are visible from outside the resulting Instance. Consequently, they can become a concrete target for AssociationRelations. If this is not desired, i.e., the composite element should exclusively exist within its "wrapping" element, then the Composition must be private. Note that Nodes in Compositions can have Compositions and so on...: The privacy acts in this case like a filter and is parsed starting from the root of an Instance. So the first "private" Compositions makes all subsequent ones private as well.

  • Because a Node can occur in different Compositions, the Composition has a role that serves as named handle of the composite instances (just like a relation name).

See also

Constructors

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constructor()
constructor(dataID: Long? = null, uri: String = "", role: String = "", target: String = "", isPublic: Boolean = false, node: Node? = null)

Properties

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var dataID: Long?

Technical database (JPA) identifier used for relation joins. The dataID is system specific and not exported to XML. It must not be used to identify elements in distributed use-cases. It should not be used to identify elements from outside the service. All model elements provide other suitable identifiers to be used.

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var isPublic: Boolean

Boolean value if the Composition is public or private. See the Composition class documentation for more information. Public Composition types and their instances are listed in the Fragments Header.

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var node: Node?

Backlink for faster traversal. This is not the composite Node but the Node owning the Composition.

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val role: String

The role name the composite elements are referred by, i.e., the name of the composition relation. The role must be unique in the scope of the Node owning the Composition.

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val target: String

The URI specifying the composite Node element. The target node must be part of the same Model as the Node specifying this composition. A modicio URI is defined as a "xs:anyURI" base with the schema extension "modicio:.*"

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val uri: String

The URI uniquely identifying the composition in the scope of its Model. A modicio URI is defined as a "xs:anyURI" base with the schema extension "modicio:.*"

Functions

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