Reference Type (Core Services)
Reference types define the way in which two elements can relate to one another. The following system defined reference types are available by default:
Defines a 'n..n' strong reference type which will be used to create hierarchical relationships. This is the default reference type when no reference type is specified. This reference type additionally requires unique names.
Defines a '1..n' composition reference type which will be used to create compositional hierarchies.
Defines a 'n..n' weak reference type.
Additional reference types that are defined by applications or users can be specified using their names.