Geography is not only concerned with space and neither is GML. The temporal.xsd schema (see http://schemas.opengis.net/gml/3.1.1/base/temporal.xsd ) contains a set of useful definitions for time related objects and properties. The simplest of these is TimeInstant.
A TimeInstant is what it says – an instant in time. It has a single child (property) called timePosition. A TimeInstant is thus written:
1 2 3 | <TimeInstant> <timePosition>1876-08-01</timePosition> </TimeInstant> |
Of course not all times are instants – some are TimePeriods. For these we can write:
1 2 3 4 5 6 7 8 9 10 11 12 | <TimePeriod> <begin> <TimeInstant> <timePosition>1876-08-01</timePosition> </TimeInstant> </begin> <end> <TimeInstant> <timePosition>1876-08-02</timePosition> </TimeInstant> </end> </TimePeriod> |
Of course GML can provide a number of ways of expressing time durations and time lengths as well and can deal with non-ISO times and dates (need a Geological Calendar?) but that is beyond our scope for now.
Leave a Reply