OSI/MHS Gateway Programmatic Interface (GPI) Reference Manual

OSI/MHS Gateway Programmatic Interface (GPI) Reference Manual—522223-001
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Information Architecture and Data
Structures
The GPI information architecture defines the structure of X.400 communications that a
client application creates, interprets, and transfers to or from the GPI service. The basic
components of this architecture are attributes and objects.
Attributes and Objects
An attribute is a fundamental item of information. An object consists of a set of
attributes. For example, a message object consists of attributes defining the message
content, the priority for sending the message, and many other items of information about
the message.
When your client program creates or copies an object, or reserves an inbound
communication, the GPI assigns an object identifier to the new object. You use this
object identifier to refer to the object in calls to procedures that operate on it. For
example, to transfer an object out to the output queue, you specify its object identifier.
(The object identifier is an integer encoded with information that is meaningful to the
GPI software and is not an ASN.1 object identifier.)
An attribute consists of its type, a syntax, and one or more values.
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The attribute type is a category indicating the purpose of the attribute’s values. For
example, priority is a type of attribute with a value indicating the priority for
sending the message.
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A syntax is a category for the form of a value. Boolean and integer are examples of
attribute syntax.
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A value is an item of information representing a characteristic or property of the
object of which it is part. For example, the value of the priority attribute indicates
whether the priority is normal, low, or urgent.
For more information about how you describe an attribute, see Attribute Descriptors
on
page 2-2.
Classes of Objects
A class is a category of objects. The purpose and internal structure of an object are
defined by its class. Each class has one or more attribute types that can appear in