D.1.1 Service-object pair class UID

Each Service Class Definition defines one or more functionally-related Service-Object Pair (SOP) Class definitions which specify well-defined operations and/or notifications which may be performed between peer DICOM Application Entities to provide an application-level service. Each SOP Class, identified by a SOP Class UID, is defined by the union of one Information Object Definition (IOD) and a specific set of one or more DIMSE Services called the DIMSE Service Group (DSG) in that

⎯ The IOD defines the data structures

⎯ The DSG defines the operations and/or notifications that can be performed on this data structure.

Two SOP Classes defined by a single Service Class Definition may differ by the IOD, the DSG or both. Two different IODs shall not, however, be part of the same SOP Class. Figure D.1.1-1 shows the relationships between Service Classes, IODs, DSGs and SOP Classes.


Notes: 1. Two examples of Service Classes are the Storage and Study Management Service Classes. The Storage Service Class relates to image Information Object Definitions such as CT, MR etc. and the Study Management Service Class relates to the Study Information Object Definition. 2. For readers familiar with OSI terminology, the concept of the Managed Object Class is the equivalent to the DICOM Service-Object Pair Class. The SOP Class specifies both the data (Attributes defined in the Information Object Definition) and the methods (Operations and Notifications (DSG) defined in the Service Class).

By setting the Abstract Syntax Name to a specific SOP Class UID value, DICOM Application Entities may negotiate Service Class operations and/or notifications for each defined SOP Class individually.