Table of Contents
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Introduction

4Science has developed the integration with the COAR system. The application can receive and send messages concerning items with externl systems. The LDN system is the protocol of message exchanging; the Quality Assurance system is the mechanism used to approve or reject item updates.

How to enable

Configuration properties involved:

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If false the LDN inbox is disabled, so the system is not “listening”

Relation with the Quality Assurance Correction Service

The LDN system, as a message exchanging i/o system, has an inbox and an outbox. Every LDN message refers to a Notify Service: all the Notify Services are configured manually from the admin application form. A Notify Service is just like an authority labelled on LDN messages.

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The match between LDN message type and the QAEvent topic is configured onto ldn-coar-notify.xml spring file. Every LDN message type has an action related, which owns a list of actions. An action is often an email to be sent and an LDNProcessor to call. The LDN processor receives the QAEvent topic as a parameter and creates the relative QAEvent.

LDN Autodiscovery mechanism

Third party system can retrieve the location of the repository LDN InBox via the LDN autodiscovery mechanism, nevertheless to be able to interact with DSpace they need to be approved by a Repository Administrators and listed in the LDN Services Directory (see next paragraph); otherwise their messages will be flagged as untrusted and not processed at all.

LDN Services Directory

You need to register the external services to trust incoming LDN messages:

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Untrusted LDN messages are not processed.

LDN Inbox queueing

LDN incoming messages are stored into the ldn_message database table. The incoming LDN messages is stored into a logical queue. The queue_status column of the table contains the status of the LDN message inside the queue. If valued as queued the LDN message will be processed. The LDN Message Extractor is an asynchronous DSpace task that reads the oldest manageable LDN message and route it to be processed; the extractor instance ends as soon as the LDN message extracted is routed and processed or failed to be.

Please consider that this means that the corresponding QAEvent is not automatically created! The corresponding QAEvent is created by the processor instance of the LDN message, invoked by the extractor.

LDN message processing

All the possible incoming LDN messages patterns are documented in the official link: COAR Notify Protocol: Notification Patterns Every LDN message json ends with the array named Type. Inside the DSpace spring configuration settings we store a list of LDN message types to be routed to certain processors. See dspace/config/spring/api/ldn-coar-notify.xml the bean ldnRouter and its incomingProcessors map property. When the extractor finds an LDN message with a Type mismatching any of the processors, the LDN message queue status moves to unmapped.

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The Timeout looks for timed-out LDN messages with queue_status as processing. If attempts < ldn.processor.max.attempts the message is enqueued again, moving its status to queued; otherwise its status is set to failed.

Offer, Acknowledgement and Announce

Considering these possible scenarios here at: COAR Notify Protocol: Example Scenarios

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When Offer message has been followed by a related Announce incoming message, there are no boxes of this kind shown, because it’s expected for the boxes about suggestions to be shown!

Automatic meaning

Automatic is a flag true/false of Inbound Patterns and are strictly linked to item filter. The Inbound Pattern is inbound from the NotifyService point of view. So they are configuration for LDN messages of the DSpace outbox. Automatic triggers an Outbox LDN message targeting the Notify service and targeting the item in submission. The automatic flag involves only the submission phase of an item. If no item filter is set - the flag is applied on all submissions.

Level of Trust

It’s a number 0 < # < 1. Triggers an automatic approval of QAEvent once the LDN message is extracted. On qaevents.xml spring configuration files the bean qaScoreEvaluation describes three different boundaries defaults to manage the level of trust:

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>= approval accepts the QAEvent automatically, so nobody will see it from the Quality Assurance Page because it’s created and right after approved.

Test calls

Here’s the Postman collection for test purposes: 

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