This document discusses potential enhancements to OWL-Time. It notes that OWL-Time currently uses Allen's temporal model and represents time positions using the Gregorian calendar only. It proposes a generalization that would allow OWL-Time to indicate and use other temporal reference systems like geological time scales or non-Gregorian calendars. This would support more temporal representations like coordinates on a timeline or ordinal named intervals, while retaining interval logic and avoiding changes to existing OWL-Time users and data.

1. Simon Cox
16 September 2015
LAND AND WATER
OWL-Time and enhancements
Briefing for Spatial Data on the Web Working Group

2. OWL-Time and enhancements | Cox2 |

3. Allen’s temporal model
OWL-Time and enhancements | Cox3 |

4. OWL-Time and enhancements | Cox4 |
“2015-03-10T17:10:00.00+01:00”^^xsd:DateTime
gYear, gMonth, gDay tied to Gregorian Calendar
No way to use (or even indicate) other temporal reference systems
e.g. geologic time, GPS/Unix time, Hebrew calendar, archeological periods, dynastic systems …

5. Generalization to enable other time systems
OWL-Time and enhancements | Cox5 |
No change to existing rdf instances!

6. Summary
• OWL-Time is based on rigorous temporal calculus, supporting
ordering of events
• All of Allen’s temporal relations are supported for ‘ProperIntervals’
• Time position in OWL-Time is limited to Gregorian calendar
would drive technical and cultural users elsewhere 
• Proposed generalization supports
• Indication of a temporal reference system (externally described)
• more representations:
Coordinate (number on timeline), ordinal values (named intervals)
• Interval logic is retained, no change for existing OWL-Time users
OWL-Time and enhancements | Cox6 |