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ACDH-CH Linked Open Date Entities Unit of Time (LODE: Unit of Time)
Linked Open Data
Linked Open Date
Time Ontology in OWL
Wikidata ontology
unit of time
ACDH-CH Linked Open Date Entities Unit of Time (LODE: Unit of Time) is an entity model/schema to describe the units of time for ACDH-CH Linked Open Date Entities (LODE). It specifies the classes for LODE. For example, the concept of the 2nd milliennium (Date Entity) is an instance of (the concept of) millinnium (Unit of Time Entity). Please see also the overall description and specifications of the two models/schemas in the ACDH-CH Linked Open Date Entities ( Unit of Time is based on the ontolgical structure of Wikidata for the purpose of interoperability. However, in order to avoid debates on the ontology and to capitalise the simple structure and loose semantic of SKOS, we simply replace all its proprietary properties with the skos:broader and skos:narrower and a few properties from Time Ontology in OWL. rdf:type relations between Unit of Time and Date Entity (see above) remains the same.

##### URI syntax #####
URI syntax consists of:
base URI
unit of time entity (1st letter is capitalised) Millennium

Unit of Time Entities uses English and mekes the URI syntax as intuitive as possible:

The entitiy for each day should looke like:
Duration should look like:

##### Known issues #####
Due to the restrictions on our technical setup, the data modelling may not be 100% right. In particular, we set skos:Concept as the rdf:type of all entities, as well as owl:Class and rdfs:subClassOf time:ProperInterval and skos:Concept. Although this may not be the best modelling (e.g. rdf:type of skos:Concept would be redundant), it is currently required to display the entities. Therefore, strict semantic reasoning may not be recommended until we can find a better solution in the future.

##### Our solution for the known issues #####
For our design, we have deliverately separated acdhdate:conceptScheme from acdhut:conceptScheme, thus have not tried to merge them. which might be a solution. Although we try to make LODE as stable as possible, we are aware that the modelling is neither perfect nor complete. Still, we decided to provide LODE: Unit of Time, because it is important to publish the data and lookup service in order to let the users know the initiative and, more importantly use URIs regardless the imperfect modelling.

We try to minimise the impact of known issues by making the data modelling explicit and transparent. In particular, this webpage ( and the website for LODE ( serve as a documentation to explain our modelling principles. In this way, users can understand the issues and develop and adjust their applications to meet their needs. In addition, we aim to improve the data modelling over time. Please contact us if you have suggestions.

##### Contact #####
LODE is created with agile development by design. As it is a living service, we prefer to develop it with the users. Any feedback (bugs, suggestions, supports, collaborations) are welcome to improve it: Thank you!
Go Sugimoto
Klaus Illmayer
Hannes Pirker
Ksenia Zaytseva
Monday, February 3, 2020 00:00:00
Wednesday, February 12, 2020 00:00:00
Saturday, December 26, 2020 00:00:00

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