This parameter used in an A-ASSOCIATE request or indication shall consist of a list containing one or more presentation contexts. Each item shall contain three components, a presentation context identification, an Abstract Syntax Name, and a list of one or more Transfer Syntax Names.
The presentation context identification components of this parameter exist to distinguish presentation contexts in communication. Such an identification of presentation context(s) applies only within the context of a given association (i.e. different presentation contexts may be identified by the same presentation context identification on different associations). It is the association-requestor's responsibility to assign an arbitrary, but unused identifier for each proposed presentation context on a given association. There is no restriction on the ordering of the presentation contexts in relation to their identifiers.
Note: A separate presentation context will be associated with each Abstract Syntax Name in each of the elements of the Presentation Context Definition List parameter. If the same Abstract Syntax Name occurs more than once, a separate and distinctly identified presentation context will be generated for each occurrence (as only one Transfer Syntax per presentation context can be accepted).
Abstract Syntaxes defined by this standard and used by DICOM Application Entites are defined in PS 3.4. Transfer Syntaxes defined by this standard and used by DICOM Application Entities are defined in PS 3.5. Further discussion on Abstract Syntaxes and Transfer Syntaxes can be found in Annex B.