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Allen's theory of time and action [All83,All84] has intervals as primitive temporal elements and assumes a linear model of time. A set of thirteen mutually exclusive binary relations - , , , , , ,
, , , , , ,
- describe different ways of relating two convex intervals. In [AF94] all these thirteen relations are formally defined using the single primitive relation *Meets*. The logic has three types of temporal entities - properties, processes and events. These entities differ in the subintervals over which they hold.^{} Thus, properties are homogeneous, events are discrete and processes are either homogeneous or heterogeneous. The 2-place predicate -
- specifies that property holds over the interval . Another predicate -
- denotes that an event occurs over an interval . Finally,
denotes that a process occurs over an interval .

Darsana Josyula
2006-01-16