Help:Property constraints portal/Contemporary

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Two entities linked through a property with contemporary constraint (Q25796498) must be contemporary, that is, must coexist at some point in history. Properties with this constraint are called contemporary properties.

There are two main categories of contemporary properties:

  1. Those requiring use, synchronous communication or direct physical interaction. For instance, uses (P2283), doctoral advisor (P184), conflict (P607), spouse (P26), etc.
  2. Those describing the relative location. For instance, located in the administrative territorial entity (P131), country (P17), located in or next to body of water (P206), location (P276), etc.

If, for practical reasons, this constraint is used in other properties, then it should never be defined as mandatory and a list of exceptions should be managed.

When are two entities contemporary?[edit]

Formally, two entities and are contemporary if, and only if, their life intervals intersect, .

The life interval of an entity is the closed interval bounded by its start time and its end time, .

The start time is the minimum acceptable value of all statements on using start properties date of birth (P569), inception (P571), start time (P580) or point in time (P585). Values with deprecated rank are ignored. If there are no valid statements using these properties, then .

The end time is the maximum acceptable value of all statements on using end properties date of death (P570), dissolved, abolished or demolished (P576), end time (P582) or point in time (P585). Values with deprecated rank are ignored. If there are no valid statements using these properties, then .

In boolean algebra (Q173183) and most programming languages, two entities and are contemporary if, and only if, .

Violation[edit]

When two entities and are not contemporary, , but are linked through a contemporary property, then there is a violation of the contemporary constraint (Q25796498).

Possible actions[edit]

There are several possible ways to address a violation of this constraint:

  • Most likely, change or remove the statement that links and through the contemporary property.
  • Fix the time value . This value should be later.
  • Fix the time value . This value should be earlier.

More[edit]

Original work about the contemporary constraint (in Spanish)

The contemporary constraint was created, analyzed and implemented as an academic project by David Abián titled Contemporary constraint: definition and implementation in a knowledge base (doi:10.13140/RG.2.2.31671.57763), which includes deeper explanations about its nature and some mathematical properties that allow to measure the quality and the temporal falsifiability of a data source.

The full text is available in Spanish on Wikimedia Commons and an scholarly article that summarizes this text will be published in English in 2019 on the occasion of The 34th ACM/SIGAPP Symposium on Applied Computing (SAC '19).