Two peer DICOM AEs implement a SOP Class of the Basic Worklist Service Class with one serving in the SCU role and one serving in the SCP role. SOP Classes of the Basic Worklist Service Class are implemented using the DIMSE-C C-FIND service as defined in PS 3.7.
Both a baseline and extended behavior are defined for the DIMSE-C C-FIND. Baseline behavior specifies a minimum level of conformance for all implementations to facilitate interoperability. Extended behavior enhances the baseline behavior to provide additional features which may be negotiated independently at Association establishment time.
The following description of the DIMSE-C C-FIND service provides a brief overview of the SCU/SCP semantics.
A C-FIND service conveys the following semantics:
— The SCU requests that the SCP perform a match for the Matching Keys and return values for the Return Keys which have been specified in the Identifier of the request, against the information that the SCP possesses, to the objects specified in the SOP Class.
Note: In this Annex, the term "Identifier" refers to the Identifier service parameter of the C-FIND service as defined in PS 3.7.
— The SCP generates a C-FIND response for each match with an Identifier containing the values of all Matching Key Attributes and all known Return Key Attributes requested. Each response contains one worklist item. All such responses will contain a status of Pending. A status of Pending indicates that the process of matching is not complete.
— When the process of matching is complete a C-FIND response is sent with a status of Success and no Identifier.
— A Refused or Failed response to a C-FIND request indicates that the SCP is unable to process the request.
— The SCU may cancel the C-FIND service by issuing a C-CANCEL-FIND request at any time during the processing of the C-FIND service. The SCP will interrupt all matching and return a status of Canceled.
Note: The SCU needs to be prepared to receive C-FIND responses sent by the SCP until the SCP finally processed the C-CANCEL-FIND request.