There are strict rules for UID formatting and usage. If these are not followed, then some modality equipment may refuse to accept MWL results containing invalid UIDs. Some of the systems are known to filter out requests for faulty UIDs.
An Application Entity (AE) is the name used in DICOM to represent a system or program running on a system which is the end-point of DICOM communications.
A Basic Film Session is a Normalised Instance which represents the whole session of Printing as requested by the SCU.
Extended negotiation allows “options” to be negotiated between 2 Application Entities as part of Negotiation.
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.