References¶

OpenAtlas uses P67 ("refers to") in order to link various entities to references.
These can be:

Documents (E31 - files, bibliographic entities or references like URLs, DOIs etc.)
Linguistic Objects (E33 - E.g. the content of a medieval charter)

In order to record which part of the document contains the respective reference a delimiter, namely a certain value to determine the position in the reference, is stored along with the link between the entities. This can be page numbers of a book, chapters, figure numbers etc.

E.g.: E31 Document "Book of Kells" - P67 "refers to" - E21 Person "Saint Mary" at delimiter: "Folio 7v"

Each reference document is more or less unique and can refer to multiple entities. The distinction is defined by the delimiter value. If the document as a whole refers to the entity, no delimiter is necessary.

Reference systems¶

e.g. vocabularies, gazetteers like GeoNames, Wikidata etc.

Users can define a reference system, i.e. an authority document (E32 "Authority Documents" https://www.cidoc-crm.org/Entity/E32-Authority-Document/Version-7.1.1) like
- name: https://www.geonames.org/
- class: E32
- description: The GeoNames geographical database covers all countries and contains over eleven million place names that are available for download free of charge.

OpenAtlas has to distinguish between
- functional web resources, implemented via an API etc.
- non digital, i.e. non web-functional ones like printed Encyclopedia, Inventory Books etc.

The link between an entity and the Authority Document would be stored in the model.link table in the following way

domain_id: ID of the Authority Document
property_code: P67
range_id: ID of the entity
description: delimiter (alphanumeric)

This combination of E32 and delimiter could furthermore be resolved as E31 "Document", as it is a unique reference documenting the entity while the E32 alone is the container for all possible references from this authority document.
E21 Person "Terry Prattchet" - is referred to by (P67) - E31 document (https://www.wikidata.org/wiki/Q46248) - P71 is listed in - E32 Authority Document (https://www.wikidata.org/wiki/)

References and files¶

Various entities can be connected to files. This is mapped as E31 (Document = file) refers to (P67) -> E1. In our case files can refer to any of the "top level" entities.
Files can (but need not necessarily) be images. Files are stored with a certain system type (i.e. file). If the file is an image, this is most probably a depiction of the entity.

A file can also have a further reference. E.g. the source where the file comes from. This is for example the bibliographical reference to the publication where a file (e.g. a scanned image) is extracted from. In this case there is a link between a document E31 with a type "Bibliography" (or sub type), via P67 to another document E31 with a system type "file". In this case the file is not the depiction of the reference but the reference is the origin of the file. This is mostly needed to document the copyright resp. right holder or source of the file.