This syntax is for a directory service distinguished name. In other words, an attribute with this syntax gives the name of an object in the directory service. X.500 calls it Distinguished-Name-Syntax. This syntax is defined in XDS as an OM class, the sole subclass of the Name OM class.
The DS will not accept a value for this attribute which could not possibly be a distinguished name in some X.500 directory service.
XDS OM object declaration:
RDNs: Object(DS-RDN), 0-n values
MATCHES FOR EQUALITY
::= { attributeSyntax 1 }