5.1 Introduction

This Part 2 of the EMC standard defines two messages that support the communication of musical work cluster information:

1. The MusicalWorkClusterNotification; and

2. The MusicalWorkClusterRequest.

In addition to these, Part 2 of the ECM standard makes use of two messages specified in Part 1, ECM Communication Protocol, namely:

3. A Manifest that may be used for communicating the messages defined in this Part 2 of the ECM message in batches; and

4. An Acknowledgment that may be used to acknowledge the receipt of a message.

This Part 2 of the standard does not define the underlying transport, network, or messaging technology used to convey these messages. This is also specified in Part 1 of the EMC standard.

Figure 1 – Choreography for the MusicalWorkClusterNotification

The message exchange defined herein occurs between one sender and one recipient. The MusicalWorkClusterNotification may serve as both the initial message and the response message (see Figure 1), ensuring a consistent and complete representation of the cluster at the time of exchange.

The MusicalWorkClusterRequest (see Figure 2) is optional and may be used in specific workflows where additional clarification of a cluster is needed. In most cases, the transmission of a MusicalWorkClusterNotification implicitly serves as a request for a response (unless the MusicalWorkClusterNotification has been sent in response to an earlier MusicalWorkClusterNotification), eliminating the need for a separate MusicalWorkClusterRequest.

However, the MusicalWorkClusterRequest can be used to explicitly request the recipient to send a MusicalWorkClusterNotification at any time. This functionality is particularly useful in scenarios where:

• An update to a previously exchanged cluster is required (e.g., for internal analysis or reconciliation purposes); and

• The requester has no information about members of the cluster for which data is requested.

In both cases, the MusicalWorkClusterRequest asks for a current snapshot of a Musical Work Cluster, enabling greater flexibility in data retrieval and synchronisation workflows.

Figure 2 – Choreography for the MusicalWorkClusterRequest

Table 1 below summarises the data exchange choreography and the points at which the messages defined in this part of the standard are sent.

Table 1 – Messages defined in Part 2 of the ECM standard