Jeni's Musings

I think that it is important to separate internal representation of temporal information and the way we communicate state of ‘the world’ and changes in ‘the world’ through various representations.

I typically use custom semantic database with built-in support for temporal dimension (additional context/scope) and basic temporal reasoning. This approach allows to keep track of changes in ‘the world’ and generate a ‘world snapshot’ at any moment in time. It is also possible to generate representation of a history of any property related to a subject (time series, collection of observations)

Complementary approach includes usage of ‘current’ and ‘historical’ properties.

For example, ‘type’ - corresponds to current type(s) of a subject, ‘type-history’ - types in history, ‘name’ - corresponds to a current name of a subject, ‘name-history’ - corresponds to a set of names that subject had at some moment in time.

Historical properties provide a very nice simplified view on a history of a subject.

If our semantic database supports also simplified reification then we can add additional assertions about time of validity for property values.

In this case, http://education.data.gov.uk/id/school/109812 corresponds to a combination of ‘current’ and ‘historical’ properties with temporal annotations.

http://education.data.gov.uk/id/school/19081/2009-09-01 can be used to reference a state of the ‘the world’ on 2009-09-01 (which also may include current-at-that-moment and historical-at-that-moment properties)

Temporal semantic databases can calculate ‘world snapshots’ more or less efficiently without assertion duplication.

In terms of inferences, this approach is more consistent with incremental inferences and truth maintenance.