Reference System

CIDOC documentation: E32 Authority Document

Reference systems can be used to link entities to external sources. A list with available reference systems is provided when clicking the Reference system button on the start page.

Linking entities to external reference systems has many advantages such as being able to find or provide more information from other sources. Futhermore, they facilitate the merge of data sets. By using reference systems LOD (Linked Open Data) can be created. Furthermore, analogue reference systems such as library catalogues or inventory numbers of a museum can be used in this way.

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

Included by default

The following reference systems are pre-installed. By using their provided APIs, OpenAtlas can provide search functionality in the respective form fields and display information about already linked entities in 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 for Wikimedia projects such as Wikipedia. Everyone is able to use the information under the CC0 public domain license.

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

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.

The GeoNames search functionality is integrated in the map search field. This enables users to automatically use the provided coordinates and identifiers for specific places.

By default it is usable for places in OpenAtlas.

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 in OpenAtlas.

Usage

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

ID

The identifier of an entity in the external reference system. For GeoNames and Wikidata IDs 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 confidence degree.

  • Close match: Concepts (here a dataset in OpenAtlas and a dataset in an external reference system) are sufficiently similar, therefore they can be used interchangeably in some information retrieval applications

  • Exact match: High degree of confidence that the concepts (a dataset in OpenAtlas and a dataset in an external reference system) can be used interchangeably

E.g. if a historical project links the city of Vienna in Wikidata, a close match would be more suitable, as the Wikidata entry deals primarily with the current city Vienna and not the historical place.

Configuration

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

  • Name - e.g. Wikipedia; the name can not be changed for the pre-installed reference systems Wikidata and GeoNames

  • Website URL - URL of the reference system (e.g. Wikidata for Wikidata)

  • Resolver URL - URL that - in combination with the ID - links to an entity in the reference system (e.g. the resolver URL https://www.wikidata.org/wiki/ in combination with the ID Q123 creates the external link: https://www.wikidata.org/wiki/Q123 (September)

  • 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 reference 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 it yet.

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