In Oracle PL/SQL, OPAQUE refers to the abstract data types whose
internal representation are maintained by Oracle. The opaque
type available in Oracle is XMLType. The XMLType data is stored
as series of bytes and Oracle does not expose this internal
representation. There are separate methods provided by Oracle to
access the OPAQUE data. A table named XMLTEST of XMLType is
created. A XML document is inserted as a whole (as a CLOB),
whose internal representation is not known. SQL> CREATE TABLE
XMLTEST OF XMLTYPE; SQL> INSERT INTO XMLTEST values 1 row
inserted. FROM xmltest i, EXTRACT(i.object_value,
'/Business/Location/Service/Basics/Attribute[Name="id"]'))) s