= Term: RelationshipType =

A type for [wiki:Relationship Relationships] between [wiki:MeshObject MeshObjects].

RelationshipType is similar to the concept of "association" in the UML, or "relationship" in information modeling. In !InfoGrid so far, a RelationshipType is always binary, i.e. its instances ([wiki:Relationship Relationships]) each connect exactly two [wiki:MeshObject MeshObjects].

A RelationshipType may either be directed or undirected. If it is directed, the source and the destination MeshObject can be distinguished by a distinct RoleType. If it is undirected, the two related [wiki:MeshObject MeshObjects] play the same RoleType.

For example, the RelationshipType `isParentOf` is directed, as there is clearly a semantic difference in whether "`A` is a parent of `B`", or "`B` is a parent of `A`". On the other hand, the RelationshipType `isRelativeOf` may be undirected, as there is no semantic difference between "`A` is a relative of `B`", and "`B` is a relative of `A`".

In InfoGrid, a RelationshipType may inherit from one or more other [wiki:RelationshipType RelationshipTypes]. Single inheritance of [wiki:RelationshipType RelationshipTypes] is common, while multiple inheritance is very rare.

See also:
 * MeshObject
 * [wiki:Relationship]
 * RoleType