OSI/MHS Gateway Programmatic Interface (GPI) Programming Guide

The GPI Library
OSI/MHS Gateway Programmatic Interface (GPI) Programming Guide—424822-001
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Object Management Procedures
GPI_STATUS_ can be used as the core for a GPI diagnostic routine. GPI diagnostics
are described in detail in Section 6, Recovering From Errors.
Object Management Procedures
After a session is established, you can use object management and message transfer
procedures. This is done within the context of outbound and inbound processing. Object
management procedures allow the client to manipulate objects in the GPI library
memory space.
You can use object management procedures to compose, decompose, inspect, and copy
objects. To understand these operations, you need a basic knowledge of objects; the
following paragraphs provide a brief introduction. A more complete description is
provided in Section 3, GPI Object Management
.
As mentioned previously, X.400 information is represented in the gateway by objects.
Objects are abstract structures based on XAPIA specifications. Objects are part of the
GPI library procedural interface, and they have no real meaning outside of this context.
They do not represent the physical organization of data in memory.
Objects are built from other abstract structures, called attributes. If an object had no
attributes, it could be regarded as an empty container; it would have a label, or object
identifier, but no contents.
Attributes represent fundamental information items. Attributes consist of a type, syntax,
and one or more values. Values are individual pieces of data. Attributes that have a
single value are called single-valued attributes. Attributes that have multiple values
are called multivalued attributes.
Information about objects and attributes is passed as parameters to GPI procedure calls.
Attribute information is passed in data structures called attribute descriptors.
Within this guide, objects are shown as shaded boxes that contain a “tree” of attributes
(Figure 2-2
). Attribute descriptors are depicted as shaded rectangles.
XAPIA specifications organize objects into classes. The classes are based on the types
of attributes that compose the objects. Different types of attributes represent different
pieces of gateway P1 and P2 information.
To build complex objects, XAPIA specifications allow small objects to be inserted as
attributes into larger ones. As a result, the attributes that represent objects can be
Figure 2-2. Object, Attribute, and Attribute Descriptor
202CDT .CDD
Attribute
Attribute
Attribute
OBJECT
Syntax
Type Value(s)
Descriptor