7 Service Overview
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# 7 Service Overview

The DICOM Message Service Element supports communication between peer DIMSE-service-users. A DIMSE-service-user acts in one of two roles:

1. invoking DIMSE-service-user

2. performing DIMSE-service-user

DIMSE-service-users make use of service primitives that are provided by the DIMSE-service-provider. The DIMSE-service-provider is an abstraction of the totality of those entities that provide DIMSE services to peer DIMSE-service-users. A service primitive shall be one of the following types:

1. request primitive

2. indication primitive

3. response primitive

4. confirmation primitive

These primitives (which are shown in Figure 7-1) are used as follows to successfully complete a DIMSE service:

- The invoking DIMSE-service-user issues a request primitive to the DIMSE-service-provider.

- The DIMSE-service-provider receives the request primitive from the invoking DIMSE-service-user and issues an indication primitive to the performing DIMSE-service-user.

- The performing DIMSE-service-user receives the indication primitive from the DIMSE-service-provider and performs the requested service.

- The performing DIMSE-service-user issues a response primitive to the DIMSE-service-provider.

- The DIMSE-service-provider receives the response primitive from the performing DIMSE-service-user and issues a confirmation primitive to the invoking DIMSE-service-user.

- The invoking DIMSE-service-user receives the confirmation primitive from the DIMSE-service-provider completing the DIMSE service.

## 7.1 Service Types

DIMSE provides two types of information transfer services that are used by DICOM Application Entities:

1. a notification service

2. an operation service

Figure 7-1. DIMSE Service Primitives

Notification services enable one DICOM Application Entity to notify another about the occurrence of an event or change of state. The definition of the notification and the consequent behavior of the Application Entities is dependent upon the Service Class and Information Object Definitions. See PS3.3 and PS3.4.

Operation services enable one DICOM Application Entity to explicitly request an operation to be performed upon a SOP Instance managed by another DICOM Application Entity.

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