Reference System

CIDOC documentation: E32 Authority Document

Reference systems can be used to link entities to external sources. You can see a list of available systems by clicking the Reference system button on the start page.

Linking entities to external reference systems has many advantages like being able to find or provide more information from other sources and it makes it a lot easier to merge/compare data from other projects using the same reference systems.

For step by step instructions to add a reference system have a look at our References Systems example.

Included by default

These systems are included in the default application. Furthermore, it was made use of their APIs to provide search functionality inside of OpenAtlas and display their information about already linked entities at the corresponding entity detail view.

Wikidata

Wikidata is a collaboratively edited multilingual knowledge graph hosted by the Wikimedia Foundation. It is a common source of open data that Wikimedia projects such as Wikipedia, and anyone else, is able to use under the CC0 public domain license.

By default it is usable for places, persons and groups.

GeoNames

GeoNames is a user-editable geographical database available and accessible through various web services, under a Creative Commons attribution license. The GeoNames database contains over 25,000,000 geographical names corresponding to over 11,800,000 unique features.

For GeoNames the search is integrated in the map search field and it is also possible to take over their coordinates for specific places.

By default it is usable for places.

GND

The GND or Gemeinsame Normdatei (translated as Integrated Authority File) is an international authority file for the organisation of personal names, subject headings and corporate bodies from catalogues. It is used mainly for documentation in libraries and increasingly also by archives and museums.

By default it is usable for persons.

Usage

Links consists of an identifier (ID) and a precision and can be entered when adding or updating an entity.

ID

The identifier of the entity in the external reference system. For GeoNames and Wikidata it will be checked for a valid format.

Precision

When linking to an external reference a precision is required. Available options are the SKOS based definitions of the confidence degree that concepts can be used interchangeable.

  • Close match: Concepts are sufficiently similar that they can be used interchangeably in some information retrieval applications

  • Exact match: High degree of confidence that the concepts can be used interchangeably

E.g. if a historical project links the city of Vienna to Wikidata, a close match would be more suitable, because the Wikidata entry is more about the current city and not the historical one.

Configuration

Admins and manager can add, update and delete external reference systems.

  • Name - e.g. Wikipedia; can not be changed for Wikidata or GeoNames

  • Website URL - an URL to the project site of the reference system

  • Resolver URL - an URL that can be linked to in combination with an ID, e.g. the resolver URL https://www.wikidata.org/wiki/ would create together with a Q123 identifier the external link: https://www.wikidata.org/wiki/Q123

  • Example ID - an example id to show the desired format e.g. Q123 for Wikidata

  • External reference match - default precision selected in forms

  • Description - a short description, shown in forms when mouse over the i icon

  • Classes - a checkbox list of available classes, for GeoNames only place is available

Classes can be removed from a system by clicking on the tab with the corresponding class name and clicking the Remove button. This button is only available if there are no entities of this class linked to the reference system.

Reference systems can be deleted only if no classes are attached to it. Wikidata and GeoNames are integrated and cannot be deleted but if desired they can be disabled by removing the classes.