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Metadata Service

tl;dr

Debug Information

Image: registry.datalab.tuwien.ac.at/dbrepo/metadata-service:1.4.7

  • Ports: 9099/tcp
  • Info: http://<hostname>:9099/actuator/info
  • Health: http://<hostname>:9099/actuator/health
    • Readiness: http://<hostname>:9099/actuator/health/readiness
    • Liveness: http://<hostname>:9099/actuator/health/liveness
  • Prometheus: http://<hostname>:9099/actuator/prometheus
  • Swagger UI: http://<hostname>:9099/swagger-ui/index.html view online

To directly access in Kubernetes (for e.g. debugging), forward the svc port to your local machine:

kubectl [-n namespace] port-forward svc/metadata-service 9099:80

Overview

The metadata service manages metadata of identities, the Broker Service (i.e. obtaining queue types), semantic concepts (i.e. ontologies) and relational metadata (databases, tables, queries, views) and identifiers.

Generation

DBRepo generates metadata for managed tables automatically by querying MariaDB's internal structures (e.g. information_schema).

Managed Tables

DBRepo only manages system-versioned tables, other tables are not supported. These other tables are ignored by DBRepo and thus can co-exist in the same database. If you want a non-system-versioned table my_table to be managed by DBRepo, make it system-versioned:

ALTER TABLE `my_table` ADD SYSTEM VERSIONING;

Then, refresh the managed table index by navigating to your database > Settings > Schema > Refresh. This action can only be performed by the database owner.

Identifiers

The service is responsible for creating and resolving a persistent identifier (PID) attached to a database, subset, table or view to obtain the metadata attached to it and allow reproduction of the exact same result.

This service also provides an OAI-PMH endpoint for metadata aggregators (e.g. OpenAIRE Graph). Through the User Interface, it also exposes metadata through JSON-LD to metadata aggregators (e.g. Google Datasets). PID metadata is always exposed, even for private databases.

The service generates internal PIDs, essentially representing internal URIs in the DataCite Metadata Schema 4.4. This can be enhanced with activating the external DataCite Fabrica system to generate DOIs, this is disabled by default.

To activate DOI minting, pass your DataCite Fabrica credentials in the environment variables:

docker-compose.yml
services:
  dbrepo-metadata-service:
    image: registry.datalab.tuwien.ac.at/dbrepo/metadata-service:1.4.5
    environment:
      spring_profiles_active: doi
      DATACITE_URL: https://api.datacite.org
      DATACITE_PREFIX: 10.12345
      DATACITE_USERNAME: username
      DATACITE_PASSWORD: password
  ...

Semantics

The service provides metadata to the table columns in the Metadata Database fromregistered ontologies like Wikidata wd:, Ontology of Units of Measurement om2:, Friend of a Friend foaf:, the prov: namespace, etc.

Limitations

  • No support for other databases than MariaDB because of system-versioning capabilities missing in other database engines.

Do you miss functionality? Do these limitations affect you?

We strongly encourage you to help us implement it as we are welcoming contributors to open-source software and get in contact with us, we happily answer requests for collaboration with attached CV and your programming experience!

Security

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