One of the challenges towards the stability of the contents in the OpenAIRE Graph consists of making its objects and their identifiers (called "OpenAIRE IDs") stable over time.
~~The barriers to this scenario are many, as the Graph keeps a map of data sources that is subject to constant variations: records in repositories vary in content, original identifiers, and persistent identifiers (PIDs), may disappear or reappear, and the same holds for the repository or the metadata collection it exposes.~~
Not only can the mappings applied to the original contents change over time, but they can also improve to catch up with changes in the input records.
One of the main issues concerns the attribution of the identity to the objects populating the Graph. The basic idea is to build the identifiers of the objects in the Graph from the related PIDs, where they are available. As a result, PIDs are collected and stored inside the respective objects (in the `pid` field).
However, although various sources can provide object-related PIDs, some of them can be "unstable". For that reason, during the process, only the PIDs available from some "authoritative", stable sources are being considered for the population of the values in the `pid` field and for the creation of the OpenAIRE IDs. OpenAIRE maintains a [list of data sources that are considered authoritative](#pid-authorities) for each specific type of PID.
~~The PID Types declared in the table below are considered to be mapped as [`result.pid`](entities/result#pid) and [`result.instance[].pid`](entities/other#pid-1) only when they are collected from a relative PID authority data source.
For each entity, we outline the PID authorities per PID Type in the [following section](#pid-authorities-per-entity).~~
There is an exception though: Handle(s) are minted by several repositories; as listing them all would not be a viable option, to avoid losing them as PIDs, Handles bypass the PID authority filtering rule.
* PIDs provided by sources that are not PID agencies (authoritative sources for a specific type of PID) are often wrong (e.g. pre-print with the DOI of the published version, DOIs with typos)
Therefore, when the record is collected from an authoritative source:
When the record is collected from a source which is _not_ authoritative for any type of PID:
* the identity of the record is forged as usual using the local identifier (typically the [oai identifier](http://www.openarchives.org/OAI/2.0/guidelines-oai-identifier.htm))
All duplicates are **merged** together in a **representative record** which must be assigned a dedicated OpenAIRE identifier (i.e. it cannot have the identifier of one of the aggregated record).
<spanclassName="todo">[TODO: the problem that this solves is that we can get a specific PID from more than one authoritative sources right ? For example, if we get DOIs from Crossref, Datacite, and Zenodo (btw Zenodo was not mentioned in the first table).
Can't we mention those sources by priority in the first table and simply mention in the text that we prefer to collect those PIDs starting from the first till the last one? Is this the problem or I am missing something else here?]</span>
When a record is aggregated from multiple sources considered authoritative for minting specific PIDs, different mappings could be applied to them and, depending on the case,
this could result in inconsistencies in the attribution of the field values.
To overcome the issue, the intuition is to include such records only once in the Graph. To do so, the concept of "delegated authorities" defines a list of datasources that
assigns PIDs to their scientific products from a given PID minter.