This operation allows an SCU which does not control a given Unified Procedure Step (UPS) instance to request to the SCP that the instance be canceled. This operation shall be invoked by the SCU through the DIMSE N-ACTION Service.
DICOM AEs that claim conformance to the UPS Push SOP Class as an SCU or an SCP shall support the Action Types and Action Information as specified in Table CC.2.2-1. DICOM AEs that claim conformance to the UPS Watch SOP Class as an SCP or claim conformance to the UPS Watch SOP Class as an SCU and choose to implement Request UPS Cancel shall support the Action Types and Action Information as specified in Table CC.2.2-1.
Request UPS Cancel – ACTION INFORMATION
|Action Type Name||Action Type ID||Attribute||Tag||Requirement Type SCU/SCP|
|Request UPS Cancel||2||Reason For Cancellation||(0074,1238)||3/1|
|Procedure Step Discontinuation Reason Code Sequence||(0074,100e)||3/1|
|>Coding Scheme Designator||(0008,0102)||1/1|
|>Coding Scheme Version||(0008,0103)||1C/1C Required if the value of Coding Scheme Designator (0008,0102) is not sufficient to identify the Code Value (0008,0100) unambiguously|
|Contact Display Name||(0074,100c)||3/1|
An SCU uses N-ACTION to request to the SCP that the state of a UPS Instance be changed to CANCELED as shown in Figure CC.1.1-1. Since all UPSs are created as instances of the UPS Push SOP Class, the Requested SOP Class UID (0000,0003) in the N-ACTION request shall be the UID of the UPS Push SOP Class. See CC.3.1 for further details.
The SCU may include a Reason For Cancellation and/or a proposed Procedure Step Discontinuation Reason Code Sequence.
The SCU may also provide a Contact Display Name and/or a Contact URI for the person with whom the cancel request may be discussed.
Note: An N-ACTION Status Code indicating success means that the Request was accepted, not that the UPS has been canceled. The system performing the UPS is not obliged to honor the request to cancel and in some scenarios, may not even receive notification of the request. See CC.2.4.
At any time after receipt of the N-ACTION-Response, the SCU may release the association on which it sent the N-ACTION-Request.
To cancel an IN PROGRESS UPS which the SCU is itself performing, the SCU shall instead use the Change UPS State action as described in CC.2.1.
The SCP shall send appropriate “UPS Cancel Requested” N-EVENT-REPORT messages, as described in CC.2.4.3 or shall report the appropriate failure response code.
Note: If provided, the Reason For Cancellation, a proposed Procedure Step Discontinuation Reason Code Sequence, a Contact Display Name and a Contact URI of someone responsible for the Cancel request might be useful in deciding to cancel the UPS or might be displayed to an operator so they can make contact for the purpose of clarifying or confirming the Cancel request. If the SCP is the performer and chooses to actually Cancel the UPS, it may at its own discretion set the Procedure Step Discontinuation Reason Code Sequence in the UPS instance based on the corresponding values provided.
If the Procedure Step State (0074,1000) of the UPS instance is still SCHEDULED, the SCP shall change the Procedure Step State, as described in CC.2.1.3, first to IN PROGRESS and then to CANCELED, ensuring that the Final State requirements, described in section CC.18.104.22.168, are met.
If the Procedure Step State (0074,1000) of the UPS instance is IN PROGRESS, and the SCP is itself the performer of the UPS, the SCP may, at its own discretion, choose to cancel the UPS as described in CC.2.1.3.
If the SCP is the performer of the UPS and chooses not to cancel, or if there is no possibility that the performing SCU will be informed of the cancel request (e.g. the subscription list for the UPS is empty, or the SCP has determined that the performing SCU has been disabled), the SCP may return a failure.
Upon completion of the N-ACTION request, the SCP shall return, via the N-ACTION response primitive, the N-ACTION Status Code applicable to the associated request as shown in Table CC.2.2-2.
Bi-directional Authentication of machines/users/applications is possible at association time (see PS 3.7 and PS 3.15). PS 3.7 provides a “Refused: Not Authorized” error code. Further requiring or documenting authentication and/or authorization features from the SCU or SCP is beyond the scope of this SOP Class.
The status values which are specific for this DIMSE operation are defined in Table CC.2.2-2.
|Success||The cancel request is acknowledged||0000|
|Warning||The UPS is already in the requested state of CANCELED||B304|
|Failure||Refused: The UPS is already COMPLETED||C311|
|Refused: Performer chooses not to cancel||C313|
|Specified SOP Instance UID does not exist or is not a UPS Instance managed by this SCP||C307|
|Refused: The performer cannot be contacted||C312|