A base for derived types used to specify complex types containing an array of objects, by unspecified UML association - either
                                 composition or aggregation.  An instance of this type contains elements representing Objects.
                                 
                                 Ideally this type would be derived by extension of AssociationType.  
                                 However, this leads to a non-deterministic content model, since both the base and the extension have minOccurs="0", and is
                                 thus prohibited in XML Schema.