OpenAIRE entity instances are created out of data collected from various data sources of different kinds, such as publication repositories, dataset archives, CRIS systems, funder databases, etc. Data sources export information packages (e.g., XML records, HTTP responses, RDF data, JSON) that may contain information on one or more of such entities and possibly relationships between them.
For example, a metadata record about a project carries information for the creation of a Project entity and its participants (as Organization entities). It is important, once each piece of information is extracted from such packages and inserted into the OpenAIRE information space as an entity, for such pieces to keep provenance information relative to the originating data source. This is to give visibility to the data source, but also to enable the reconstruction of the very same piece of information if problems arise.
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## The `DataSource` object
### id
_Type: String • Cardinality: ONE_
The OpenAIRE id of the data source, created according to the [OpenAIRE entity identifier and PID mapping policy](../pids-and-identifiers).
The OpenAIRE compatibility of the ingested research products, indicates which guidelines they are compliant according to the vocabulary [dnet:datasourceCompatibilityLevel](https://api.openaire.eu/vocabularies/dnet:datasourceCompatibilityLevel).
"description": "Recent Patents on Medical Imaging publishes review and research articles, and guest edited single-topic issues on recent patents in the field of medical imaging. It provides an important and reliable source of current information on developments in the field. The journal is essential reading for all researchers involved in Medical Imaging."
```
### subjects
_Type: String • Cardinality: MANY_
List of subjects associated to the datasource
```json
"subjects": [
"Medicine",
"Imaging",
...
]
```
### languages
_Type: String • Cardinality: MANY_
The languages present in the data source's content, as defined by OpenDOAR.
Access restrictions to the research data repository. Allowed values are: `{ feeRequired, registration, other }`.
This field only applies for re3data data source; see [re3data schema specification](https://gfzpublic.gfz-potsdam.de/rest/items/item_758898_6/component/file_775891/content) for more details.
Upload restrictions applied by the datasource, as defined by re3data.org. One of `{ feeRequired, registration, other }`.
This field only applies for re3data data source; see [re3data schema specification](https://gfzpublic.gfz-potsdam.de/rest/items/item_758898_6/component/file_775891/content) for more details.
Whether the research data repository supports versioning:
`yes` if the data source supports versioning, `no` otherwise.
This field only applies for re3data data source; see [re3data schema specification](https://gfzpublic.gfz-potsdam.de/rest/items/item_758898_6/component/file_775891/content) for more details.
The URL of the data source providing information on how to cite its items. The DataCite citation format is recommended (http://www.datacite.org/whycitedata).
This field only applies for re3data data source; see [re3data schema specification](https://gfzpublic.gfz-potsdam.de/rest/items/item_758898_6/component/file_775891/content) for more details.