A SOP Class derived from a Standard SOP Class that has been specialized in an implementation by additional Type 1, 1C, 2, 2C, or 3 Attributes, by enumeration of specific permitted values for Attributes, or by enumeration of specific permitted Templates. The additional Attributes may either be drawn from the Data Dictionary in PS 3.6, or may be Private Attributes. The enumeration of permitted Attribute values or Templates shall be a subset of those permitted in the related Standard SOP Class. Since the semantics of the related Standard SOP Class may be modified by the additional Attributes, a Specialized SOP Class utilizes a Privately Defined UID which differs from the UID for the related Standard SOP Class.
Notes: 1. Since a Specialized SOP Class has a different UID than a Standard or Standard Extended SOP Class, other DICOM implementations may not recognize the Specialized SOP Class. Because of this limitation, a Specialized SOP Class should only be used when a Standard or Standard Extended SOP Class would not be appropriate. Before different implementations can exchange Instances in a Specialized SOP Class, the implementations must agree on the UID, content (in particular the additional Type 1, 1C, 2, and 2C Attributes), and semantics of the Specialized SOP Class. A Specialized SOP Class may be used to create a new or experimental SOP Class that is closely related to a Standard SOP Class.
2. The Association Negotiation for a Specialized SOP Class may include a SOP Class Common Extended Negotiation Sub-Item (as defined in PS 3.7) for identification of the Service Class and of the Related General SOP Class from which it was specialized. This may allow a receiving application, without prior agreement on the Specialized SOP Class IOD, to process Instances of that class as if they were instances of a Related General SOP Class.