- From: James Clark <jjc@jclark.com>
- Date: Fri, 15 Sep 2000 12:09:34 +0700
- To: Ashok Malhotra/Watson/IBM <petsa@us.ibm.com>
- CC: Paul.V.Biron@kp.org, XML Schema Comments <www-xml-schema-comments@w3.org>
Ashok Malhotra/Watson/IBM wrote: > > Oh boy! I just looked at the draft and realized there is no discussion > of a value space for recurringDuration. Thank you, James, for catching > this. My apologies for the omission. Paul, we need to fix this. > > Let me take a stab at defining the value space for recurringDuration: > "The value space for recurringDuration is a series of timeDurations > that recur with some frequency. The frequency of recurrence is defined > as the timeDuration between two occurrences." Each member of the value space is a series. Thus the value space is itself a set of series. The members of each series in the value are surely timePeriods not timeDurations (they start at a particular instant of time, and persist for a particular duration). Only a series that satisfies the following constraints can be members of the value space: - fixed duration: the duration of each member of the series must be the same - fixed period: the duration from the start of one member to the start of another member must be the same for any two consecutive members of the series - infinite: every member has a preceding and a following member In other words it is a single duration of time that recurs starting at a series of equally-separated instants of times. A single period of time is modelled as an infinite series with a zero period. The lexical space represents the value space by representing the start of one the time periods that is a member of the series. The choice of which time period to represent is arbitrary. Thus <recurringDuration duration="P0Y1M" period="P1Y">2000-01-01T00:00:00</recurringDuration> represents the same value as <recurringDuration duration="P0Y1M" period="P1Y">2001-01-01T00:00:00</recurringDuration> I find it hard to see how you can pick a single canonical lexical representation. Perhaps recurringDuration should be abstract. James
Received on Friday, 15 September 2000 01:42:15 UTC