References and Relationships

    ref_type    : local_ref | remote_ref
    local_ref   : 'lref' '<' type_name '>'
    remote_ref  : ref_kind '<' type_name '>'
    ref_kind    : 'ref' | 'set' | 'bag' | 'list'
    relationship_dcl : 'relationship' ref_kind 
            '<' type_name '>' [ 'inverse' scoped_name ] 
            [ 'ordered_by' scoped_name ]

References are similar to pointers in a memory-based language such as Pascal or C. A local_reference( lref for short) is a pointer to another value in the same object. The type_name can designate any value type. A remote_reference is a set of zero or more pointers to other objects. The type_name must designate an object type (interface), called the target type of the relationship. A ref points to zero or one objects, a set points to zero or more distinct objects, and a bag or list points to zero or more objects that are not necessarily distinct (that is, a bag or list contains the identity of each object zero or more times). Lists are not supported.