Open temporal intervals

[rybesh]

EDTF Level 1 provides expressions for open intervals of time, i.e. intervals that do not have a beginning, or that do not have an end. These are distinguished from intervals for which either the beginning or end is simply not known. The latter are easily modeled using the Time Ontology as time intervals for which the beginning or end is left unstated: under the open world assumption, if nothing is said about an endpoint of an interval, that just means we know nothing about it, not that it doesn’t exist.

Open intervals, however, are trickier, because of that same open world assumption. Simply omitting the missing endpoint would make open intervals indistinguishable from intervals with an unknown endpoint. Instead, we want to express that the interval does not have an endpoint, not that we do not know anything about the endpoint.

For this purpose the draft EDTF Ontology defines two subclasses of time:ProperInterval for modeling open intervals:

• edtfo:OpenBeginningInterval
• edtfo:OpenEndInterval

The former adds the constraint that instances must have zero time:hasBeginning values, while the latter adds the constraint that instances must have zero time:hasEnd values.

Examples:

• level-1/open-end-interval-day-precision.ttl
• level-1/open-start-interval-day-precision.ttl