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CIP Message Communications Appendix D
Terminology
In CIP specifications, “Object,” “Class,” “Instance,” “Attribute” and “Service” are defined as follows:
Specifying an Object Address (Request Path)
This is the basic concept involved in accessing an Object or Attribute.
Each Object Class has a “Class ID”.
There are two types of “Class ID”; one is standardized by ODVA and the other is decided independently by
each device vendor.
Each Object Instance also has ID. This is called “Instance ID.” Different Instance ID is assigned to each Object.
As for Object Class standardized by ODVA, Instance ID is given to it according to the ODVA method. On the
other hand, vendor's own Instance ID is decided independently by the vendor.
Each Attribute also has “Attribute ID.”
Each Object is accessed to by using “Class ID,” “Instance ID,” and “Attribute ID.”
In the device, you can designate Object by specifying these three IDs.
When requesting “Service,” you should specify “Class ID,” “Instance ID,” and “Attribute ID.” (Instance ID and
Attribute ID may not be required, depending on the Service.)
The “Class ID,” “Instance ID,” and “Attribute ID” identify a location in the device and are known as the request
path.
Term Meaning
Object An abstract representation of a particular component within a product.
Class A set of objects that all represent the same kind of system component. A class is a generalization of an
object. All objects in a class are identical in form and behavior, but may contain different attribute values.
Instance A specific and real (physical) occurrence of an object. For example: New Zealand is an instance of the object
class Country. The terms Object, Instance, and Object Instance all refer to a specific Instance.
Attribute A description of an externally visible characteristic or feature of an object. Typically, attributes provide status
information or govern the operation of an Object. For example: the ASCII name of an object; and the repeti-
tion rate of a cyclic object.
Service A function supported by an object and/or object class. CIP defines a set of common services and provides for
the definition of Object Class and/or Vendor Specific services.
Attribute 1
Class ID = 1
Attribute = 3
Attribute 2
Attribute 3
Attribute 4
Instance ID = 1
Instance ID = 1
Class ID = 2
Device