metadata-service.md

author: Martin Weise

tl;dr

!!! debug "Debug Information"

Image: [`registry.datalab.tuwien.ac.at/dbrepo/metadata-service:1.4.5`](https://hub.docker.com/r/dbrepo/metadata-service)

* 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`

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

Most of the metadata available in DBRepo is generated automatically, leveraging the available information and taking the burden away from researchers, data stewards, etc. For example, the schema (names, constraints, data length) of generated tables and views is obtained from the information_schema database maintained by MariaDB internally.

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:

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.

!!! question "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](../../contact) with us, we happily answer requests for collaboration with attached CV and your programming 
experience!

Security

(none)