Documentation

h1. Instance

An instance is one specific materialization or version of the result. For example, you can have one result with three instances as result of deduplication: 

* one is the pre-print

* one is the post-print

* one is the published version

Each instance is characterized by the properties described in the following table.

|_. field name |_. cardinality |_. type |_. description |

| *accessright* | ONE | [[AccessRight]] | Maps "dc:rights":https://www.dublincore.org/specifications/dublin-core/dcmi-terms/elements11/rights/, describes the access rights of the web resources relative to this instance. |

| *alternateIdentifier* | MANY | [[ControlledField]] | All the identifiers associated to the result other than the authoritative ones |

| *articleprocessingcharge* | ONE | [[APC]] | The money spent to make this book or article available in Open Access. Source for this information is the OpenAPC initiative. |

| *license* | ONE | string | License URL |

| *pid* | MANY | [[ControlledField]] | The set of persistent identifiers associated to this instance that have been collected from an authority for the pid type (i.e. Crossref/Datacite for doi). See [[OpenAIRE_entity_identifier_and_PID_mapping_policy]] for more information. |

| *publicationdate* | ONE | string | Date of the research product |

| *refereed* | ONE | string | describes if this instance has been peer-reviewed or not. Allowed values are peerReviewed, nonPeerReviewed, UNKNOWN (as defined in https://api.openaire.eu/vocabularies/dnet:review_levels) |

| *type* | ONE | string | The specific sub-type of this instance (see https://api.openaire.eu/vocabularies/dnet:result_typologies following the links) |

| *url* | MANY | string | URLs to the instance. They may link to the actual full-text or to the landing page at the hosting source. |