Part of the maintenance process involves retirement of sections of the Standard, including but not limited to, IODs, Attributes, Service Classes, SOP Classes, Transfer Syntaxes and Protocols.
Retirement does not imply that these features cannot be used. However, the DICOM Standards Committee will not maintain the documentation of retired features. The reader is referred to earlier editions of the Standard.
The use of the retired features is deprecated in new implementations, in favor of those alternatives remaining in the standard.