The Implementation Identification information allows implementations of communicating AEs to identify each other at Association establishment time. It is intended to provide non-ambiguous version identification in the event of communication problems encountered between two nodes.
A Composite Instance is the official DICOM term for a persistent storable object.
Every object in DICOM, whether a permanent Composite Object or merely a transient Normalised Object as used in Printing has a unique UID called its Instance UID.
The Well-Known UIDs are Static Instance UID mostly used in normalised operations. The following is a list of all UIDs in DICOM
One of the irritating features of DICOM for small and medium scale developers is the need to obtain an official UID prefix to use for both software implementations and for images and related objects.