An
object type is a user-defined composite datatype created in the database. A
column can represent an object type or a row can represent an object type. An
instance of the Object type can be stored in the database. This object instance
can be fetched to the client side and modified using Oracle Objects for OLE.
There are two types of objects instance.
· If a column represents
an object type, then an instance of this object type is referred as an embedded
instance or a value instance. For example, an
ADDRESS object type is stored as a column in the PERSON table. They can be
embedded within other structures. An embedded instance or a value instance can
also be the attributes of another object instance. In OO4O, object instance of
this type are represented by an OraObject object.
· If a row in an object
table represents an object type, then the instance of this type is referred to
as a referenceable object. An internally
referenceable object has an unique object identifier. This unique object
identifier is represented by the REF data type. A REF column can be thought of
as a pointer to a referenceable object. OO4O applications can retrieve a REF to
a referenceable object, fetch (pin) the associated referenceable object to the
client side, and update (flush) the modified referenceable object to the
database. In OO4O, an object instance of this type represented by an OraRef
object.
The following topics provide more information:
·Using the OraObject Interface·Retrieving an Embedded/Value Instance from the Database
·Accessing
Attributes of an Embedded/Value Instance
·Modifying
Attributes of an Embedded/Value Instance
·Using the
OraRef Interface·Retrieving a REF from the Database
·Accessing
Attributes of a Referenceable Instance
·Modifying
Attributes of a Referenceable Instance