Re: Time ontology in PDDL

From: Drew McDermott (
Date: 10/28/02

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       >  > Why do we need both *second* and *sec*?  (etc.)  What does
       >   *DayOfWeek* denote exactly?  I realize that they are introduced in
       >   connection with time intervals that lie on "official" boundaries,
       >   such as next Friday, as opposed to some random 24-hour period.  I
       >   just don't see how the extra temporal units contribute.  If we start
       >   with an "era" (such as CE(..)), and carve intervals out by first
       >   getting the n'th year, then the m'th day of that year, and so forth,
       >   we can use the original units to keep track of how long each
       >   interval is.  That's what happens in my version, which lacks all
       >   temporal units except *second*, *minute*, *hour*, *day*, *week*,
       >   *month*, and *year*.  I could make it look more like the original if
       >   I understood the original.
       What about the day that starts at 3pm on a Thursday and ends at 3pm 
       on the following Friday (like the LeMans 24 hour race) ?
    That is indeed a day, according to the ontology, but it's not the nth
    day of any month or year.  Nonetheless, its duration is the same as
    those "aligned" days.
                                                 -- Drew

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