Knowledge Systems Laboratory, Stanford University
10
Functions on Time-Interval
uStarting-Point and Ending-Point
„ (=> (and (Time-Point ?s) (Time-Interval ?i))
„       (<=> (Starting-Point ?i ?s)
„                (and (not (exists ?j (and (Time-Point ?j)
„                                                     (Before ?j ?s)
„                                      (Point-In-Interval ?j ?i))))
„                        (=> (Time-Point ?p)
„                              (not (exists ?k (and (Time-Point ?k)
–                                               (Before ?k ?p)
„                                                               (Point-In-Interval ?k ?i))))
„                              (or (Equal-Point ?p ?s) (Before ?p ?s)))))))
uDuration
„Convex time interval
>Time quantity whose magnitude is the difference between the location of the interval’s ending point and starting point
„Non-convex time interval
>Sum of durations of all convex time intervals contained in it